ORGANIC COMPOUNDS - I : MCQs & SHORT ANSWERS

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

1. Which of the following is not a functional group containing oxygen ?
   
   
   
   1. Alcohol
   2. Aldehyde
   3. Ketone
   4. Halide
      
   
   
2. The formula of methanal is ______.
   
   
   
   1. HCHO
   2. CH₃CH₂OH
   3. CH₃COCH₃
   4. CH₃COOCH₃
      
   
   
3. Which of the following is propanone ?
   
   
   
   1. CH₃OH
   2. CH₃CH₂COOH
   3. CH₃COCH₃
   4. CH₃COOCH₃
      
   
   
4. The formula of the functional group ester is ______.
   
   
   
   1. -CHO
   2. -COOH
   3. -COOR
   4. -CONH₂
      
   
   
5. Which of the following represents alcohol group ?
   
   
   
   1. -OH
   2. -COOH
   3. -CHO
   4. -CONH₂
      
   
   
6. The formula of butanol is ______.
   
   
   
   1. CH₃OH
   2. C₂H₅OH
   3. C₃H₇OH
   4. C₄H₉OH
      
   
   
7. Fermentation process to manufacture ethyl alcohol is ______.
   
   
   
   1. an aerobic process
   2. an anaerobic process
   3. a polymerization process
   4. a catalytic aerobic process
      
   
   
8. Which enzyme converts sugar (sucrose) or molasses into glucose or fructose ?
   
   
   
   1. Invertase
   2. Zymase
   3. Ethanol
   4. Ptylin
      
   
   
9. Which enzyme converts glucose ( or fructose) onto alcohol ?
   
   
   
   1. Ptylin
   2. Invertase
   3. Zymase
   4. Lactose
      
   
   
10. Yeast contains ______.
    
    
    
    1. invertase only
    2. zymase only
    3. both invertase and zymase
    4. neither invertase nor zymase
       
    
    
11. Pure ethanol is ______.
    
    
    
    1. acidic
    2. basic
    3. neutral
    4. acidic base
       
    
    
12. The chemical name of acetic acid is ______.
    
    
    
    1. methanoic acid
    2. ethanoic acid
    3. propanoic acid
    4. vinegar
       
    
    
13. Ethylethanoate is ______.
    
    
    
    1. an alcohol
    2. an acid
    3. an ester
    4. a ketone
       
    
    
14. ______ have fruity smell.
    
    
    
    1. Alcohols
    2. Organic acids
    3. Esters
    4. Ketones
       
    
    
15. In aldehydes, the carbonyl group is attached to
    
    
    
    1. one hydrogen and one oxygen
    2. one hydrogen and one alkyl group
    3. two alkyl groups
    4. one oxygen and one alkyl group
       
    
    
16. The boiling point of formaldehyde is ______°C.
    
    
    
    1. 10
    2. 20
    3. 40
    4. 80
       
    
    
17. Which catalyst is used for the reduction of methanal to methanol.
    
    
    
    1. Pd
    2. Pt
    3. V₂O₅
    4. K₂Cr₂O₇
       
    
    
18. What is the boiling point of acetone ?
    
    
    
    1. 40°C
    2. 48°C
    3. 56°C
    4. 64°C
       
    
    
19. Which of the following is immiscible with water ?
    
    
    
    1. Ethanol
    2. Formaldehyde
    3. Acetone
    4. Hexane
       
    
    
20. Oxidation of propanone in presence of alkaline KMnO₄ gives ______.
    
    
    
    1. ethanal
    2. ethanol
    3. ethanoic acid
    4. ethylethanoate
       
    
    
21. Which of the following is an IUPAC name ?
    
    
    
    1. Propanoic acid
    2. Ethyl alcohol
    3. Formic acid
    4. Acetaldehyde
       
    
    
22. What is vinegar ?
    
    
    
    1. Methanol
    2. Ethanol
    3. Formic acid
    4. Acetic acid
       
    
    
23. The boiling point of acetic acid is ______ °C.
    
    
    
    1. 98
    2. 108
    3. 118
    4. 128
       
    
    
24. An organic acid + an alcohol → ______ + water.
    
    
    
    1. An aldehyde
    2. A ketone
    3. An ester
    4. A carboxylic acid
       
    
    
25. What is used as a food preservative ?
    
    
    
    1. Ethanol
    2. Propanone
    3. Formic acid
    4. Acetic acid
       
    
    
26. Which of the following is artificial rubber ?
    
    
    
    1. Neoprene
    2. Isoprene
    3. Chloroprene
    4. TEFLON
       
    
    
27. The monomers of condensation polymer contain minimum ______ functional group/groups.
    
    
    
    1. 1
    2. 2
    3. 3
    4. 4
       
    
    
28. The name of thje functional group -OH is ______.
    
    
    
    1. aldehyde
    2. ketone
    3. alcohol
    4. glucose
       
    
    
29. Which of the following is the functional group present in ketone compounds ?
    
    
    
    1. -CHO
    2. -OH
    3. C=C
    4. >C=O
       
    
    
30. Which compound has "-anal" in the end of its name ?
    
    
    
    1. -CHO
    2. -OH
    3. >C=O
    4. C-C
       
    
    
31. The enzyme which converts milk into curd is ______.
    
    
    
    1. Lactase
    2. Invertase
    3. Zymase
    4. Cellulase
       
    
    
32. Which of the following is not an oxidising agent ?
    
    
    
    1. NaBH₄
    2. KMnO₄
    3. Cr₂O₃
    4. Fehling's solution
       
    
    
33. The reaction between carboxylic acid and ethanol in presence of H₂SO₄ is known as ______.
    
    
    
    1. saponification
    2. hydrolysis
    3. esterification
    4. decarboxylation
       
    
    
34. Which functional group does not give a compound having two carbon atoms ?
    
    
    
    1. Carboxylic acid
    2. Aldehyde
    3. Ketone
    4. Alcohol
       
    
    
35. Which of the following is a condensation polymer ?
    
    
    
    1. Nylon
    2. PVC
    3. Natural rubber
    4. Teflon
       
    
    
36. The respsctive aldehyde obtained from methane is ______.
    
    
    
    1. methanol
    2. formic acid
    3. formaldehyde
    4. ethanol
       
    
    
37. 5% aquaous solution of ethanol is known as...
    
    
    
    1. formalin
    2. vinegar
    3. denatured alcohol
    4. rectified spirit
       
    
    
38. Tollen's reagent is...
    
    
    
    1. Ammoniacal silver nitrate
    2. Silver nitrate
    3. Ammonium nitrate
    4. Ammonium chromate
       
    
    
39. Which gas is produced during fermentation ?
    
    
    
    1. CO
    2. CO₂
    3. Cl₂
    4. O₂
       
    
    

ANSWERS TO MCQs

(1) D (2) A (3) C (4) C (5) A (6) D (7) B (8) A (9) C (10) C (11) C (12) B (13) C (14) C (15) B (16) B (17) A (18) C (19) D (20) C (21) A (22) D (23) C (24) C (25) D (26) A (27) B (28) C (29) D (30) A (31) A (32) A (33) C (34) C (35) A (36) C (37) D (38) A (39) B (40)

SHORT QUESTIONS

ANSWER IN SHORT:

1. What are hydrocarbons ?
   
        ANS : The compounds containing atoms of carbon and hydrogen only are called hydrocarbons.
   


2. What is a functional group ?
   
        ANS : An atom or a group of atoms which is responsible for chemical reactions of organic compounds is called a functional group. OR An atom or a group of atoms present in a compound which is responsible for the chemical properties of that compound is called a functional group.
   


3. Organic compounds containing same functional group show similar chemical properties. True or false ?
   
        ANS : This is a true statement.
   


4. Ethane reacts more rapidly than ethyne. True or false ?
   
        ANS : This is a false statement.
   


5. What is the general formula of alcohols ?
   
        ANS : The general formula of alcohols is C_nH_{2n + 1}OH or R-OH where R represents the alkyl group (C_nH_{2n + 1}) and n=1,2,3,...
   


6. Write the formula of ethanoic acid.
   
        ANS : The formula of ethanoic acid is CH₃COOH.
   


7. Mention first four alkanes.
   
        ANS : Methane, ethane, propane and butane are first four alkanes.
   


8. Mention first four alcohols.
   
        ANS : Methanol, ethanol, propanol and butanol are first four alcohols.
   


9. By which two methods can ethyl alcohol (ethanol) be prepared ?
   
        ANS : Ethyl alcohol can be prepared by (i) Fermentation of carbohydrates (ii) Hydration.
   


10. Which enzyme converts milk into curd ?
    
         ANS : Lactase converts milk into curd.
    


11. What does lactase do during the conversion of milk into curd ?
    
         ANS : Lactase converts lactose into lactic acid.
    


12. What is fermentation ?
    
         ANS : Fermentation is a slow process of breaking down of carbon compounds in the presence of enzymes amd in the absence of oxygen.
    


13. Write the reaction of hydration of ethene.
    
         ANS :
    
    
    


14. What is the boiling point of pure ethanol ?
    
         ANS : The boiling point of pure ethanol is 78°C.
    


15. Write the equation for the combustion of ethanol.
    
         ANS :
    
    
    


16. Write the formula of sodium ethoxide.
    
         ANS : The formula of sodium ethoxide is CH₃CH₂ONa.
    


17. What is obtained when ethanol reacts with sodium metal ?
    
         ANS : When ethanol reacts with sodium metal; sodium ethoxide and hydrogen are obtained.
    


18. What is the formula of ethanal ?
    
         ANS : The formula of ethanal is CH₃CHO.
    


19. What is the formula of ethylethanoate (ethyl acetate) ?
    
         ANS : The formula of ethylethanoate is CH₃COOCH₂CH₃.
    


20. Write the IUPAC name of CH₃C₂H₅.
    
         ANS : Ethylethanoate.
    


21. What is esterification ?
    
         ANS : The process in which an alcohol reacts with an organic acid to form an ester in presence of a small amount of conc. sulphuric acid is called Esterification.
    


22. What is 'rectified spirit' ?
    
         ANS : Ethyl alcohol containing 5% water is called 'rectified spirit'.
    


23. What is 'Denatured' ethyl alcohol ?
    
         ANS : 'Denatured' ethyl alcohol is the ethyl alcohol to which poisonous methanol or CuSO₄ has been added to prevent people from consuming it.
    


24. Write symbolically the functional group 'carbonyl'.
    
         ANS : The functional group carbonyl is >C=O.
    


25. Write the formula of formaldehyde (methanal).
    
         ANS : The formula of formaldehyde is
    
    
    


26. Write the formula of acetone.
    
         ANS : The formula of acetone (propanone) is
    
    
    


27. Write the common as well as IUPAC name of the compound whose formula is HCHO.
    
         ANS : The common name of HCHO is formaldehyde and its IUPAC name is methanal.
    


28. Write the common names of first four aldehyde compounds.
    
         ANS : The common names of first four aldehyde compounds are : formaldehyde, acetaldehyde, propionaldehyde and butyraldehyde.
    


29. Write the chemical formula of butanal.
    
         ANS : The chemical formula of butanal is CH₃CH₂CH₂CHO.
    


30. Write the common name of methanal and propanone.
    
         ANS : The common name of methanal is formaldehyde and that of propanone is aceton.
    


31. Which catalyst is used to prepare formaldehyde from methanol ?
    
         ANS : Silver oxide, Ag₂O is used as catalyst to prepare formaldehyde from methanal
    


32. Write the chemical equation of oxidation of methanol to methanal.
    
         ANS :
    
    
    


33. What does oxidation of methanal yield ?
    
         ANS : The oxidation of methanal yields methanoic acid.
    


34. Mention the oxidising agents used for the oxidation of methanal.
    
         ANS : Tollen's reagent, potassium permanganate solution, solution of potassium dichromate, etc rae used as oxidising agents for the oxidation of methanal.
              [The Gujarati version of text book (GSEB) mentions two names : Ammoniacal silver nitrate (Tollen's reagent) and Fehling's reagent].
    


35. Write the chemical formula of methanal cyanohydrin.
    
         ANS : The formula of methanal cyanohydrin is
    
    
    


36. What is formalin ?
    
         ANS : Formalin is 30-35 % aqueous solution of formaldehyde.
    


37. Name the process by which acetone (propanone) is prepared.
    
         ANS : Acetone is prepared by Fischer-Tropsch process.
    


38. Which catalyst is used in Fischer-Tropsch process to prepare acetone ?
    
         ANS : Cobalt oxide (CoO) is used as catalyst in Fischer-Tropsch process to prepare acetone.
    


39. What is the formula of iso-propyl alcohol (2-propanol) ?
    
         ANS : The formula of iso-propyl alcohol is
    
    
    


40. What is the formula of acetone cyanohydrin ?
    
         ANS : The formula of acetone cyanohydrin is
    
    
    


41. Write the general formula of carboxylic acid (organic acids).
    
         ANS : The general formula of carboxylic acids is
    C_nH_{2n + 1}COOH [n=0,1,2,3,...].
    


42. What is the common name of methanoic acid ?
    
         ANS : The common name of methanoic acid is formic acid.
    


43. Which bacteria convert ethanol into acetic acid ?
    
         ANS : Acetobactor convert ethanol into acetic acid.
    


44. Which catalyst is used in the preparation of acetic acid from methanol.
    
         ANS : I₂-Rh (Iodine-rhodium) is used as a catalyst in the preparation of acetic acid from methanol.
    


45. Acetic acid is immiscible with water. True or false ?
    
         ANS : This is a false statement.
    


46. Write the equation showing reaction between acetic acid and sodium metal.
    
         ANS :
    
    
    


47. What is neutralisation reaction ?
    
         ANS : A neutralisation reaction is the one in which an acid reacts with a base to form a salt and water.
    


48. Give the example of the neutralisation reaction of acetic acid.
    
         ANS :
    
    

    CH₃COOH + NaOH → CH₃COONa + H₂O

    .
    


49. What is sodalime ?
    
         ANS : Sodalime is a mixture of NaOH and CaO in the ratio of 3:1 (NaOH + CaO).
    


50. What is produced when acetic acid reacts with sodalime ?
    
         ANS : Methane and carbon dioxide are produced when acetic acid reacts with sodalime.
    


51. What is decarboxylation reaction ?
    
         ANS : The removal of carbon dioxide (-COO part) from the carboxyl group of an organic acid is called decarboxylation reaction.
    


52. What is vinegar ?
    
         ANS : Vinegar is 4 to 6 % aqueous solution of acetic acid.
    


53. What do we mean by man-made materials ?
    
         ANS : New substances prepared from the natural raw materials are called man-made materials.
    


54. What are polymers ?
    
         ANS : Polymers are long-chain compounds with many smaller units called monomers.
    


55. Mention some synthetic fibres.
    
         ANS : Rayon, nylon, polyester, etc. are synthetic fibres.
    


56. Give some examples of plastics.
    
         ANS : Polythene, polyvinylchloride (PVC), TEFLON, Bakelite, melamine, etc. are examples of plastics.
    


57. How rae polymers classified ?
    
         ANS : Polymers are classified on the basis of the reaction of their formation into 'Addition polymer' and 'Condensation polymer'.
    


58. What is the chemical name of TEFLON ?
    
         ANS : The chemical name of TEFLON is Polytetrafluoroethene.
    


59. What is an addition polymer ?
    
         ANS : Addition polymers are formed by addition of one or more than one (same or different) unsaturated monomer having double or triple bond.
    


60. Mention monomers of natural rubber and artificial rubber.
    
         ANS : Isoprene is the monomer of natural rubber and chloroprene is the monomer of artificial rubber.
    


61. Write the formula of isoprene.
    
         ANS : The formula of isoprene is
    
    
    


62. Write the formula of butadiene.
    
         ANS : The formula of butadiene is CH₂=CH-CH=CH₂.
    


63. What is used as an alternative to rubber ?
    
         ANS : Polybutadiene is used as an alternative to rubber.
    


64. What is the formula of chloroprene ?
    
         ANS : The formula of chloroprene is
    
    
    


65. Give examples of addition polymers.
    
         ANS : Polythene, PVC, rubber, polybutadiene, etc. are examples of addition polymers.
    


66. From what is natural rubber obtained ?
    
         ANS : Natural rubber is obtained from the latex of rubber trees.
    


67. What are the defects of natural rubber ?
    
         ANS : Natural rubber has low elasticity and low strength (it is less tough).
    


68. Between which temperature range is the elasticity of natural rubber maintained ?
    
         ANS : The elasticity of natural rubber is maintained between 10°C to 60°C.
    


69. What is the effect of temperature on natural rubber ?
    
         ANS : Natural rubber becomes brittle below 10°C and soft above 60°C.
    


70. What is vulcanisation of rubber ?
    
         ANS : Vulcanisation of rubber is the process in which rubber is mixed with sulphur powder and heated upto 100 - 140°C.
    


71. Why is rubber vulcanised ?
    
         ANS : Rubber is vulcanised to improve its properties of elasticity and hardness.
    


72. What is a condensation polymer ?
    
         ANS : A polymer formed by the condensation of two or more than two monomers with the elimination of a simple molecule like water or ammonia, is called condensation polymer.
    


73. Give examples of condensation polymer.
    
         ANS : Polyester and polyamides are examples of condensation polymer.
    


74. Which types of compounds react to form polyester ?
    
         ANS : A compound containing two carboxylic acid groups and another compound containing two hydroxyl groups react to form polyester.
    


75. Which types of compounds react to form polyamides ?
    
         ANS : A compound containing two carboxylic acid groups and another compound containing two amino groups react to form polyamides.
    


76. Nylon is an addition polymer. True or false ?
    
         ANS : This is a false statement.
    


77. Nylon is a polyamide. True or false ?
    
         ANS : This is a true statement.
    


78. What is soap ?
    
         ANS : Soap is a sodium or potassium salt of higher fatty acids like stearic acid or palmitic acid.
    


79. What is saponification ?
    
         ANS : saponification is a process of making soap by reaction between a vegetable oil and sodium hydroxide.
    


80. What are (synthetic) detergents chemically ?
    
         ANS : Chemically detergents are sodium salts of sulphonates.
    


81. Mention the functional groups of soap and detergent.
    
         ANS : The functional group of a soap is -COONa and that of a detergent is -SO₃Na.
    


82. Which are two parts of a soap or detergent ?
    
         ANS : A long chain of hydrocarbon which is nonpolar and water-repelling and -COONa (in soap) or -SO₃Na (in detergent) which is polar and has affinity for water are the two parts of a soap or detergent.
    


83. Which functional group is present in the following compounds ? (i)CH₃CH₂CH₂OH (ii) CH₃COCH₃ (iii) CH₃CHO (iv) CH₃CH₂COOH (v) CH₃CH₂CH=CH₂.
    
         ANS : (i) Alcohol (ii) ketone (iii) aldehyde (iv) carboxylic acid (v) hydrogen.
    


84. Which gas is produced during the process of fermentation ?
    
         ANS : Carbon dioxide gas is produced during the process of fermentation.
    


85. Which compound is obtained during the hydration of ethene ?
    
         ANS : Ethyl alcohol is obtained during the hydration of ethene.
    


86. Write the names of products of oxidation reaction of ethanol in presence of KMnO₄ and chromium oxide.
    
         ANS : The product obtained by oxidation of ethanol in presence of KMnO₄ is ethanoic acid whereas in presence of chromium oxide we get ethanal.
    


87. Write the equation of the reaction of reduction of methanal.
    
         ANS :
    
    
    


88. What is obtained as by-product during preparation of soap ?
    
         ANS : Glycerol is obtained as by-product during preparation of soap.
    


89. How can you convert propanone to ethanoic acid ?
    
         ANS : Propanone can be converted to ethanoic acid by its oxidation using alkaline potassium permanganate.
    


90. Define detergent.
    
         ANS : A chemical substance used to remove dirt from the surface of anything is called a detergent.
    


91. What are glycerides ?
    
         ANS : Glycerides are ester compounds present in animal fat or vegetable oils.
    


92. Which two enzymes are present in yeast ?
    
         ANS :Invertase and zymase are two enzymes present in yeast.
    

NON-METALS - III : LONG ANSWERS

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

1. Mention physical properties of nonmetals.
   

   ANS :
   

   
   
   • Nonmetals occur in all three states : solid, liquid and gas.
     
   • They are neither malleable nor ductile.
     
   • They do not conduct heat and electricity because they do not have free electrons (graphite is an exception).
     
   • They are lustreless.
     
   • They are hard and brittle.
     
   • They generally have low melting points and boiling points.
     
   • They are light in weight.
     
   • Solid nonmetals do not produce ringing sound.
     

   
   

   
   
2. Explain chemical properties of nonmetals.
   

   ANS : Nonmetals are electronegative elements because they accept electrons and form negatively charged ions. For example, oxygen forms negative oxide ion O^-2 by accepting two electrons.
   

   1/2 O₂ + 2 e^- → O^-2
   1/2 Cl₂ + e^- → Cl^-
   

   
   
   REACTION WITH OXYGEN : Nonmetals form either acidic oxide or neutral oxide with oxygen.
   

   
   
   • When carbon burns in air, it forms carbon dioxide which is an acidic oxide.
     

     C_(s) + O_2(g) → CO_2(g)
     

     
     
     Carbon dioxide dissolves in water to form carbonic acid [H₂CO₃].
     

     CO_2(g) + H₂O_(l) → H₂CO_3(aq)
     

   
   
   
   • When sulphur burns in air, it reacts with oxygen to form sulphur dioxide which is an acidic oxide.
     

     S_(s) + O_2(g) → SO_2(g)
     

     
     
     Sulphur dioxide dissolves in water to form sulphurous acid [H₂SO₃]
     

     SO_2(g) + H₂O_(l) → H₂SO_3(aq)
     

   
   
   
   • Phosphorus forms phosphurus pentoxide (2P₂O₅) with oxygen which dissolves in water to form phosphoric acid [H₃PO_4(aq)].
     

     P_4(s) + 5O_2(g) → 2P₂O_5(g)
     
     2P₂O_5(g) + 6H₂O → 4H₃PO_4(aq)
     

   
   
   • Oxides like CO, N₂O, H₂O are neutral oxides as their aqueous solutions are neither acidic nor basic or they do not have any effect on any litmus paper.
   
   

   
   
   REACTION WITH ACIDS : Nonmetals do not react with dilute acids as they are not able to displace hydrogen from acids.
   
   REACTION WITH CHLORINE : Nonmetals form chlorides with chlorine. These chlorides are either liquid or gas.
   
   
   
   REACTION WITH HYDROGEN : Nonmetals form covalent hydrides with hydrogen.
   
   
   
   Methane (CH₄), hydrochloric acid (HCl), etc. are hydrides of nonmetals.
   



3. Describe the Importance of nonmetals.
   

   ANS :
   

   
   
   • Hydrogen gas reacts with nitrogen to form ammonia gas.
     
   • Carbon is used in the preparation of useful substances like gunpowder, sugar, cold drinks, dry ice, urea, etc.
     
   • Oxygen supports life on earth.
     
   • Nitrogen is used in the preparation of nitric acid, nitroglycerin(explosives) and nitrogenous fertilisers.
     
   • Sulphur is used in the preparation of paper pulp, fungicides, etc.
     
   • Phosphorus is used in making matchsticks, insecticides, etc.
     

   
   

   
   
4. Write a few sentences on Hydrogen.
   

   ANS :
   

   
   
   • Hydrogen was discovered in 1766 AD by English chemist Cavendish.
     
   • Its chemical symbol is H.
     
   • It is the lightest of all elements.
     
   • It is the first element of the periodic table.
     
   • Hydrogen does not occur in free state (monoatomic molecule) in the atmosphere.
     
   • It is a diatomic molecule.
     
   • it is a colourless, odourless gas.
     
   • It is present in outer space.
     
   • It is the main element present in sun.
     

   
   

   
   
5. Describe preparation of hydrogen in laboratory.
   

   ANS :
   
   
   AIM : To prepare hydrogen gas in laboratory.
   
   APPARATUS & MATERIAL : Conical flask, Thistle funnel, glass container, bee-hive shelf, glass jar, glass tube, zinc granules, hydrochloric acid, water, etc.
   
   PROCEDURE :

   
   
   • Zinc granules are taken in conical flask and the equipment is set up as shown in figure.
     
   • Dilute hydrochloric acid is added slowly to the flask through thistle funnel.
     

   
   
   OBSERVATION : The reaction between zinc granules and dilute hydrochloric acid produces hydrogen gas which is collected by downward displacement of water in an inverted jar.
   
   CHEMICAL REACTION :
   
   Zn_(s) + 2HCl_(aq) → ZnCl_2(aq) + H_2(g)
   
   NOTE : In place of dilute HCl we can also use dilute H₂SO₄.
   
   Zn_(s) + H₂SO_4(aq) → ZnSO_4(aq) + H_2(g)
   

   
   
6. Describe manufacture of hydrogen from natural gas.
   

   ANS :
   

   
   
   • Hydrogen gas is manufactured on large scale from natural gas by steam reforming process.
     
   • Methane (the main constituent of natural gas) is mixed with steam and passed over nickel catalyst at 800°C and 30 atm pressure.
     
   • The reaction produces carbon dioxide and hydrogen.
     
     
     
   • Hydrogen gas can also be obtained by the electrolysis of acidified water.
     

   
   

   
   
7. Describe chemical properties of hydrogen.
   

   ANS :
   

   
   
   1. Hydrogen gas burns in air (oxygen) with a blue flame forming watervapour.
      
      2H_2(g) + O_2(g) → 2H₂O_(g)
   
   
   
   2. It burns in chlorine to form white fumes of hydrogen chloride gas.
      
      H_2(g) + Cl_2(g) → 2HCl_(g)
      
      Similarly it forms hydrogen fluoride gas with fluorine.
      
      H_2(g) + F_2(g) → 2HF_(g)
      
   
   
   
   3. It forms hydrides with metals like lithium, sodium and calcium.
      
      H_2(g) + 2Li_(s) → 2LiH_(s)
      
      H_2(g) + 2Na_(s) → 2NaH_(s)
      
      H_2(g) + Ca_(s) → CaH_2(s)
   
   
   
   4. Hydrogen reduces oxides of those metals, which are less reactive, to free metals. Thus, when hydrogen is passed over hot copper oxide copper metal and water are produced.
      
      CuO_(s) + H_2(g) → Cu_(s) + H₂O_(l)
   
   

   
   



8. Write a detailed note on ammonia, its manufacture, properties and uses.
   

   ANS :
   AMMONIA : Ammonia is a very important industrial chemical as it is used for the manufacture of a wide range of chemicals. It is manufactured commercially by Haber's process.
   
   MANUFACTURE : A mixture of nitrogen and hydrogen in the ratio of 1 : 3 is heated under 200 - 300 atm pressure in presence of catalyst (finely divided iron + molybdenum) at about 450 °C. The reaction is reversible.
   
   
   
   PHYSICAL PROPERTIES :
   

   
   
   • It is a colourless gas.
     
   • It has characteristic pungent smell which irritates eyes and nose.
     
   • It is poisonous.
     
   • It is highly soluble in water.
     

   
   
   CHEMICAL PROPERTIES :
   

   
   
   • Ammonia reacts with hydrochloric acid to form ammonium chloride.
     
     NH_3(g) + HCl_(l) → NH₄Cl_(s)
     
     
   • Ammonia decomposes in presence of electric discharge.
     
     
     
     
   • Ammonia reacts with oxygen in presence of catalyst platinum at 1073 K to form nitric oxide.
     
     
     
     
   • Aqueous solution of ammonia acts as a base. [NOTE : This property is given as physical property in the text book]
     

   
   
   USES :
   

   
   
   • In the manufacture of fertilisers such as urea, ammonium nitrate and ammonium sulphate.
     
   • In the manufacture of nitric acid.
     
   • In the manufacture of baking soda and washing soda.
     
   • In the manufacture of some medicines such as para-aminobenzoic acid (PABA), folic acid, etc.
     
   • In the preparation of dyes and explosives.
     

   
   

   
   
9. Describe Extraction of Sulphur.
   

   ANS : Pure sulphur is obtained by (i)Frasch Process or (ii) from natural gas and oil by chemical process.
   
   FRASCH PROCESS : The process is used to obtain pure sulphur from the sulphur bed in the ground. It is based on the fact that sulphur has relatively low melting point.
   
   

   
   
   • A hole of about 30 cm diameter is bored upto the sulphur bed.
     
   • Three concentric pipes of different diameters are descended upto sulphur deposits.
     
   • Pressurised superheated water at about 170°C is forced down through the outermost pipe. The heat of water melts the underground sulphur.
     
   • Hot compressed air is passed through the innermost pipe.
     
   • A mixture of molten sulphur and water comes out through central pipe.
     
   • The sulphur-water emulsion is allowed to settle in settling tanks. Yellow solid sulphur separates from water after cooling. This sulphur is 99.5% pure.
     

   
   
   FROM NATURAL GAS AND OIL :
   

   
   
   • Sulphur compounds in natural gas and oil are first converted into hydrogen sulphide. (H₂S).
     
   • Hydrogen sulphide is heated in presence of oxygen to obtain sulphur dioxide.
     
   • This sulphur dioxide is then heated with additional hydrogen sulphide in the presence of catalyst Fe₂O₃ to obtain sulphur in free state.
     
     
     

   
   

   
   
10. Write a note on Allotropes of sulphur.
    

    ANS :
    

    
    
    • Different arrangement of molecules in the crystals give rise to allotropes of sulphur.
      
    • There are two allotropes of crystalline sulphur. (i)Rhombic sulphur and (ii) Monoclinic sulphur.
      
    • Rhombic sulphur is stable below 96°C and its crystals have octahedral shape.
      
    • Monoclinic sulphur is stable above 96°C and its crystals are needle-shaped.
      
    • As one allotrope changes into another at 96°C, it is called TRANSITION TEMPERATURE for sulphur.
      
    • Both allotropes have similar chemical properties but their physical properties differ due to their different physical structures.
      
    • When solid sulphur is heated its molecular chain breaks which on further heating yields viscous liquid sulphur. This on heating starts boiling.
      

    
    

    
    
11. Mention Chemical properties of sulphur.
    

    ANS :
    

    
    
    • Sulphur burns with blue flame and produces sulphur dioxide.
      
      

      S_(s) + O_2(g) → SO_2(g)

      
      
      
    • REACTION WITH ACIDS : Sulphur is oxidised to sulphur dioxide when it reacts with hot and concentrated sulphuric acid.
      
      

      S_(s) + 2 H₂SO_4(aq) → 2H₂O_(l) 3SO_2(g)

      
      
      Sulphur is oxidised to sulphuric acid when it reacts with hot and concentrated nitric acid.
      
      

      S_(s) + 6HNO_3(aq) → H₂SO_4(aq) + 6NO_2(g) + 2H₂O_(g)

      
      
      
    • REACTION WITH CARBON : Sulphur reacts with carbon at high temperature to give carbon disulphide.
      

      C_(s) + 2S_(s) → CS_2(l)

      
      
      
    • REACTION WITH HYDROGEN : When hydrogen gas is passed through boiling sulphur, foul smelling hydrogen sulphide gas is formed.
      

      S_(s) + H_2(g) → H₂S_(g)

      
      

    
    

    
    
12. Mention uses of sulphur.
    

    ANS :
    

    
    
    • In the manufacture of sulphuric acid.
      
    • As an antiseptic in skin ointments for skin treatment and in cosmetics.
      
    • For making dyes, matches, gunpowder, pulp of paper and fireworks.
      
    • In vulcanisation of rubber.
      
    • For manufacturing carbon disulphide which is a solvent.
      
    • As a disinfectant, fungicide, germicide, etc. for destroying bacteria, fungi, insects, etc.
      
    • In printing (dyeing) of clothes.
      

    
    

    
    
13. Write a detailed note on sulphur dioxide.
    

    ANS : The reaction of sulphur with oxygen gives sulphur dioxide.
    
    

    S_(s) + O_2(g) → SO_2(g)

    
    
    PHYSICAL PROPERTIES :
    

    
    
    • It is a colourless gas.
      
    • It has a pungent smell.
      
    • It is a pollutant gas which causes acid rain due to dissolution in rain water.
      

    
    
    CHEMICAL PROPERTIES :
    

    
    
    • Sulphur dioxide dissolves in water to form sulphurous acid (H₂SO₃).
      
      

      SO_2(g) + H₂O_(l) ↔ H₂SO_3(aq)

      
      
      
    • Sulphur dioxide reacts with aqueous sodium hydroxide to form sodium sulphite (Na₂SO₃).
      

      SO_2(g) + 2NaOH_(aq) → Na₂SO_3(aq) + H₂O_(l)

      
      
      
    • When sulphur dioxide gas is passed through lime-water, the solution turns cloudy due to the formation of insoluble calcium sulphite (CaSO₃).
      
      

      SO_2(g) + Ca(OH)_2(aq) → CaSO_3(s) + H₂O_(l)
      

      
      
      
    • When sulphur dioxide gas is passed through an aqueous solution of hydrogen sulphide, it turns milky (turbid) due to formation of colloidal sulphur.
      
      

      SO_2(g) + 2H₂S_(aq) → 3S_(s) + 2H₂O_(l)

      
      
      
    • Sulphur dioxide combines with oxygen in presence of catalyst vanadium pentoxide [V₂O₅] at 450°C to form sulphur trioxide.
      
      
      

    
    
    USES :
    

    
    
    • For the manufacture of sulphuric acid.
      
    • As a preservative in orange and lemon squashes and jams.
      
    • For bleaching of wood pulp in paper industry.
      

    
    

    
    
14. Describe manufacture of sulphuric acid by Contact Process.
    

    ANS : The contact process is divided into different stages and uses various units such as sulphur burner, precipitator, steam scrubber, drying tower, arsenic purifier, contact chamber and absorption unit.
    
    PREPARATION OF SO₂ : SO₂ is obtained by burning sulphur or pyrites.
    

    Δ
    S_(s) + O_2(g) → SO_2(g)
    

    
    CONVERSION OF SO₂ into SO₃ IN CONTACT CHAMBER : The mixture of purified SO₂ and air is passed over catalyst vanadium pentoxide [V₂O₅] to produce SO₃.
    
    
    
    ABSORPTION OF SO₃ IN CONC. H₂SO₄ : SO₃ obtained from the contact chamber is dissolved in concentrated H₂SO₄ acid giving oleum, H₂S₂O₇. [Oleum is also known as 'fuming sulphuric acid'.]
    
    
    
    Sulphuric acid of any concentration can be obtained by diluting oleum with water.
    
    

    H₂S₂O_7(l) + H₂O_(l) → 2H₂SO_4(aq)

    
    
    Contact process yields sulphuric acid which is pure and of about 100% strength.
    

    
    
15. Write physical properties, chemical properties and uses of sulphuric acid.
    

    ANS :
    PHYSICAL PROPERTIES
    

    
    
    • Concentrated sulphuric acid is colourless viscous liquid containing 98% H₂SO₄ and 2% water.
      
    • Concentrated sulphuric acid is a powerful water-absorbing agent.
      
    • Dilute sulphuric acid contains 10% H₂SO₄ and 90% water.
      

    
    CHEMICAL PROPERTIES
    

    
    
    • Concentrated sulphuric acid dehydrates sugar to carbon. The black mass of carbon is called sugar charcoal and the reaction is called charring of sugar.
      
      
      
      
    • Dilute sulphuric acid reacts with metals like zinc and iron to form metal sulphates and hydrogen gas.
      
      Zn_(s) + H₂SO_4(aq) → ZnSO_4(aq) + H_2(g)
      
      Fe_(s) + H₂SO_4(aq) → FeSO_4(aq) + H_2(g)
      
      
    • Sulphuric acid is strong dibasic acid from which two hydrogen atoms can be displaced in solution.
      
      H₂SO_4(l) + 2H₂O_(l) → 2H₃O⁺_(aq) + SO_4(aq)^-2
      

    
    USES
    

    
    
    • In the preparation of fertilisers.
      
    • In the manufacture of pigments, dyes and paints.
      
    • In the preparation of detergents.
      
    • In storage batteries.
      

    
    

    
    
16. 
    

    ANS :
    

    
    

NON-METALS - II : BRIEF ANSWERS

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

1. Explain with example : Reaction of nonmetals with chlorine.
   

   ANS: Nonmetals form chlorides with chlorine. These chlorides are usually in gaseous state.
   
   
   



2. Explain with example : Reaction of nonmetals with hydrogen.
   

   ANS: Nonmetals form covalent hydrides with hydrogen.
   
   
   
   Methane (CH₄), hydrochloric acid (HCl), etc. are hydrides of nonmetals.
   



3. Mention physical properties of hydrogen.
   

   ANS:
   

   
   
   • It is lighter than air.
     
   • It is a colourless, tasteless and odourless gas.
     
   • It is insoluble in water.
     
   • It is neutral gas (it does not change the colour of litmus paper).
     

   
   

   
   
4. Mention uses of hydrogen.
   

   ANS:
   

   
   
   • Hydrogen Welding : When an electric arc is passed through hydrogen, it splits into atoms which release large amount of heat when they recombine to form molecules. This heat is used to melt and join (weld) the metals.
     
   • In the manufacture of ammonia by Haber's process.
     
   • In the manufacture of methanol and hydrochloric acid.
     
   • Liquid hydrogen is used as a fuel in space shuttles.
     
   • In the manufacture of vegetable ghee.
     

   
   

   
   
5. Mention physical properties of sulphur.
   

   ANS:
   

   
   
   • It is pale yellow solid crystalline substance which exists in different forms called allotropes.
     
   • It is odourless and tasteless.
     
   • It is insoluble in water.
     
   • It is soluble in organic solvents like carbon disulphide, toluene (methyl
     benzene), etc.
     

   
   

   
   
6. 
   

   ANS:
   

   
   

NON-METALS - I : MCQs & SHORT ANSWERS

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

1. There are ______ nonmetals.
   
   
   
   1. 20
   2. 22
   3. 24
   4. 25
      
   
   
2. How many nonmetals are in solid state ?
   
   
   
   1. 11
   2. 12
   3. 13
   4. 14
      
   
   
3. How many nonmetals are in gaseous state ?
   
   
   
   1. 7
   2. 8
   3. 9
   4. 10
      
   
   
4. The atomic number of sulphur is...
   
   
   
   1. 15
   2. 16
   3. 17
   4. 18
      
   
   
5. Which of the following is used as a fuel in space rockets ?
   
   
   
   1. Liquid hydrogen
   2. Liquid nitrogen
   3. Refined kerosene
   4. phenol
      
   
   
6. Sulphur belongs to _____ group in periodic table.
   
   
   
   1. Boron
   2. Carbon
   3. Oxygen
   4. Halogen
      
   
   
7. _____ ia a metalloid.
   
   
   
   1. Copper
   2. Sodium
   3. Bromine
   4. Silicon
      
   
   
8. When sulphur reacts with sulphuric acid _____ gas is produced.
   
   
   
   1. SO₂
   2. H₂S
   3. NO₂
   4. NH₃
      
   
   
9. Sulphuric acid is produced by ______.
   
   
   
   1. Ostwald process
   2. Frasch process
   3. Contact process
   4. Bessemer process
      
   
   
10. 
    
    
    
    4. 
       
    
    

ANSWERS TO MCQs

(1) B (2) A (3) D (4) B (5) A (6) C (7) D (8) A (9) C (10)

SHORT QUESTIONS

ANSWER IN SHORT:

1. Which nonmetal is in liquid state ?
   
        ANS : Bromine is the nonmetal in liquid state.
   


2. Give an example of a nonmetal which conducts heat and electricity.
   
        ANS : Graphite ( a form of carbon) conducts heat and electricity.
   


3. Why are nonmetals electronegative elements ?
   
        ANS : Nonmetals are electronegative elements because they accept electrons and form negatively charged ions.
   


4. Which type of oxides do nonmetals form ?
   
        ANS : Nonmetals form either acidic or neutral oxides.
   


5. Write formula of carbonic acid.
   
        ANS : The formula of carbonic acid is H₂CO₃.
   


6. Give examples of some neutral oxides.
   
        ANS : CO, N₂O, H₂O are examples of neutral oxides.
   


7. Why is carbon monoxide a neutral oxide ?
   
        ANS : Carbon monoxide (CO) is a neutral oxide because it forms neither acid nor base with water.
   


8. Why do nonmetals not react with dilute acids ?
   
        ANS : Nonmetals do not react with dilute acids because they are not able to displace hydrogen from acids.
   


9. Who discovered hydrogen ? When ?
   
        ANS : English chemist Cavendish discovered hydrogen in 1766 AD.
   


10. Why is ammonia a very important chemical ?
    
         ANS : Ammonia is a very important chemical because it is used in the preparation of fertilisers, nitric acid, explosives, nylon fibre, etc as well as household cleaners.
    


11. Why is ammonia not collected by downward displacement of water ?
    
         ANS : Ammonia is not collected by downward displacement of water because it is highly soluble in water.
    


12. What is the full form of PABA ?
    
         ANS : The full form of PABA is Para-Amino Benzoic Acid.
    


13. Mention important ores of sulphur.
    
         ANS : Important ores of sulphur are : Zinc blende (ZnS), gypsum (CaSO₄.2H₂O) and copper pyrites (CuFeS₂).
    


14. Write electronic configuration of sulphur ?
    
         ANS : The electronic configuration of sulphur is 2,8,6.
    


15. When SO₂ is heated with H₂S in the presence of catalyst ______, sulphur is obtained. [Fill up the blank].
    
         ANS : Fe₂O₃.
    


16. Mention two crystalline allotropes of sulphur.
    
         ANS : The crystalline allotropes of sulphur are (1) rhombic sulphur (2) monoclinic sulphur.
    


17. What is transition temperature ?
    
         ANS : The temperature at which one allotrope of an element changes into another allotrope is called TRANSITION TEMPERATURE of that element.
    


18. What is the transition temperature of sulphur ?
    
         ANS : The transition temperature of sulphur is 96°C.
    


19. What is the shape of the crystals of rhombic sulphur ?
    
         ANS : The shape of the crystals of rhombic sulphur is octahedral.
    


20. What is the shape of the crystals of monoclinic sulphur ?
    
         ANS : The shape of the crystals of monoclinic sulphur is needle-like.
    


21. What is known as the king of chemicals ?
    
         ANS : Sulphuric acid is known as the king of chemicals.
    


22. Why is sulphuric acid known as the king of chemicals ?
    
         ANS : Sulphuric acid is known as the king of chemicals because it is used to prepare many important chemical substances like fertilisers, dyes, soap, etc.
    


23. Which catalyst is used for conversion of SO₂ into SO₃ in contact chamber ?
    
         ANS : V₂O₅ is used as catalyst for conversion of SO₂ into SO₃ in contact chamber.
    


24. What is the strength of H₂SO₄ obtained by Contact process ?
    
         ANS : The strength of H₂SO₄ obtained by Contact process is about 100 %.
    


25. What is charring of sugar ?
    
         ANS : The process in which concentrated sulphuric acid converts sugar to a black mass of carbon (sugar charcoal) by dehydration is called charring of sugar.
    


26. Give names of some nonmetallic elements.
    
         ANS : Hydrogen, oxygen, nitrogen, chlorine, bromine, iodine, sulphur, phosphorus, etc. are nonmetallic elements.
    


27. Write an equation for the reaction of phosphorus pentoxide with water.
    
         ANS :

    2P₂O_5(g) + 6H₂O_(l) → 4H₃PO_4(aq)
    

    
    


28. Write the equation for the industrial production of hydrogen.
    
         ANS :

    Ni catalyst
    800°C
    30 atm
    CH_4(g) + 2H₂O -----> CO_2(g) + 4H_2(g)
    



29. By which method is ammonia gas produced ?
    
         ANS : Ammonia gas is produced by Haber's process.
    


30. Which nonmetallic element is obtained by Frasch process ?
    
         ANS : Sulphur is obtained by Frasch process.
    


31. Write chemical formula of Oleum (fuming sulphuric acid).
    
         ANS : The chemical formula of fuming sulphuric acid is H₂S₂O₇.
    


32. Which crystalline form of sulphur is most stable ?
    
         ANS : Rhombic sulphur is the most stable crystalline form of sulphur.
    


33. On which physical property of sulphur is Frasch process based ?
    
         ANS : Frasch process is based on the property of low melting point (388 K) of sulphur.
    


34. 
    
         ANS :
    

METALS - III : LONG ANSWERS

GIVE ANSWER IN DETAIL

*INDEX-TOPIC SEARCH

1. Write a note on minerals in India.
   
   ANS : [table to be posted]
   
   
2. Explain : Froth Floatation Process OR The process to concentrate sulphide ores.
   
   ANS : This method is used for the concentration of sulphide ores of copper, zinc, lead, etc.
   
   PRINCIPLE: This method is based on the principle of difference in the wetting properties of the ore and the gangue particles with water and oil.
   
   PROCESS:
   
   
   The powdered ore is mixed with water, containing small quantity of oil (pine oil or turpentine oil) in a large tank.
   The sulphide particles in the ore get wet with oil while dust and sand particles do not get wet with oil.
   The water containing ore is agitated violently by blowing air to form froth.
   Sulphide particles being lighter float along with the froth at the surface which is removed from the top of the tank and collected.
   Impurities being heavier collect at the bottom. The froth is then washed, filtered and dried.
   
   
3. Write a note on Magnetic Separation.
   
   ANS :
   
   PRINCIPLE:This method uses the principle of difference in the magnetic properties of the ore and the gangue (impurities).
   
   EQUIPMENT:
   
   
   
   A magnetic separator consists of a leather conveyer belt moving over two rollers. One of the rollers has a strong magnet in it.
   
   PROCESS: Powdered ore is dropped on the moving belt at one end through a hopper. When it reaches the other end , nonmagnetic impurities fall down first whereas the magnetic particles fall later forming a separate heap.
   
   This method is generally used for the concentration of iron ores.
   
   
4. Explain : Calcination with proper examples.
   
   ANS : Calcination is a process in which concentrated ore is heated strongly in absence of air. Calcination is generally used
   for conversion of metal carbonates and hydroxides in to their corresponding oxides and to remove volatile impurities.
   
   Examples:
   
   
   
   
5. Write a note on 'Chemical Reduction' method.
   
   ANS : The conversion of metal oxide into metal is called REDUCTION. When chemicals like carbon, carbon monoxide, aluminium, etc. are used as reducing agents, the process is called CHEMICAL REDUCTION.
   In the carbon-reduction process, the metal oxide is mixed with coke (a form of carbon) and heated in a furnace. Carbon reduces metal oxide to free metal. Oxides of zinc, iron, copper, nickel, tin and lead are reduced by this method.
   
       ZnO_(s) + C_(s) → Zn_(s) + CO_(g)
   
       Fe₂O_3(s) + 3C → 2Fe_(s) + 3CO_(g)
   
       MnO_2(s) + 2C_(s) → Mn_(s) + 2CO_(g)
   
   Carbon monoxide is also used as reducing agent.
   
       Fe₂O_3(s) + 3CO_(g) → 2Fe_(s) + 3CO_2(g)
   
   Aluminium is used as reducing agent for the reduction of certain oxides of metals like chromium, manganese and iron. A large amount of heat is produced during the process and the metal is obtained in liquid (molten) state. The process is known as THERMIT PROCESS.
   
       Cr₂O_3(s) + 2Al_(s) → 2Cr_(l) +Al₂O_3(s)
   
       3MnO_2(s) + 4Al_(s) → 3Mn_(l) + 2Al₂O_3(s)
   
       Fe₂O_3(s) + 2Al_(s) → 2Fe_(l) + Al₂O_3(s)
   
   Chemical reduction method cannot be used for highly reactive metals like sodium, potassium, aluminium, etc. Oxides of such metals are reduced by electrolytic reduction method.
   
   
6. Explain Electrochemical Reduction giving example.
   
   ANS : Oxides of highly reactive metals like sodium, potassium and aluminium cannot be reduced by using chemical reduction ( by carbon or aluminium). If carbon is used large amount of heat is required and metal carbide is formed. These metals are obtained by electrolysis of their fused (molten) salts. The cathode acts as the reducing agent as it supplies electrons to metal ions.
   
   ELECTROLYSIS OF SODIUM CHLORIDE
       In this process molten sodium chloride is taken as electrolyte in an electrolytic cell. The reactions taking place at the two electrodes are :
   

   NaCl_(l) → Na⁺ + Cl^-
   
   Na⁺ + e^- → Na_(s)
   (at cathode)
   
   Cl^- → Cl + e^-
   (at anode)
   
   Cl + Cl → Cl_2(g)

   
   
       If aqueous solution of sodium chloride is taken instead of molten sodium chloride, reduction of hydrogen ions (2H⁺) to hydrogen (H₂ gas) takes place instead of reduction of sodium ion(Na⁺) to sodium metal.
   
   
7. Explain : Reactivity Series of Metals.
   
   ANS : The series of metals in the decreasing order of their reactivities is called reactivity series of metals. Some metals like sodium and potassium are highly reactive whereas metals like copper, silver and gold have very low reactivity.
   
   The reactivities of metals can be compared by their reaction with dilute acid or by comparing their oxidation potential with the standard hydrogen potential. Based on their reaction with dilute acids the following series has been prepared :
   
   K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au
   
   The metals on the left of the hydrogen in the series are more reactive and they can displace hydrogen from acids. Metals on the right side of hydrogen are less reactive and they cannot liberate hydrogen from dilute aqueous acids.
   
   similarly, a more reactive metal can displace a less reactive metal from its solution. Thus, a strip of more reactive zinc displaces less reactive copper from aqueous copper sulphate solution (Displacement reaction). The blue colour of copper sulphate solution disappears gradually and brown granules of copper are seen at the bottom.
   
   Zn_(s) + CuSO_4(aq) → ZnSO_4(aq) + Cu_(s)
   
   If a strip of copper is placed in the solution of ZnSO₄, no chemical reaction occurs as copper is less reactive than zinc.
   
   
8. Write two equations each for obtaining metal oxides and hydroxides.
   
   ANS :
   OXIDES
   
   
   
   1. When sodium reacts with oxygen it forms sodium oxide.
      

      4Na_(s) + O_2(g) → 2Na₂O_(s)

   
   
   2. Iron reacts with steam and forms iron oxide and hydrogen gas.
      

      3Fe_(s) + 4H₂O_(g) → Fe₃O_4(s) + 4H_2(g)

   
   
   
   HYDROXIDES
   
   
   
   1. Sodium oxide reacts with water and forms sodium hydroxide.
      

      Na₂O_(s) + H₂O_(l) → 2NaOH_(aq)

   
   
   2. Magnesium reacts slowly with cold water and forms magnesium hydroxide and hydrogen gas.
      

      Mg_(s) + 2H₂O_(l) → Mg(OH)_2(aq) + H_2(g)

   
   
   
   
   
9. Give names of different steps of metallurgy and write a brief note on each step.
   
   ANS : Different steps involved in metallurgy are :
   
   
   
   • Crushing and grinding of ore
     
   • Concentration or enrichment of ore
     
   • Roasting, calcination and smelting
     
   • Reduction
     
   • Refining and purification of metals
     
   
   
   CRUSHING AND GRINDING OF ORE : The ore in the form of big rocks is broken into small pieces with the help of crushers. These small pieces are then powdered with the help of a ball mill or stamp mill.
   
   CONCENTRATION OR ENRICHMENT OF ORE : The process of removal of impurities from an ore is called ' Ore Concentration'. Different methods are employed for concentration of ore depending on the nature of ore and the impurities in it.
   
   Froth Floatation Process is used for the concentration of sulphide ores.
   
   Magnetic Separation method is used for removal impurities present in an ore with magnetic properties or for concentration of a nonmagnetic ore containing magnetic impurities.
   
   Centrifugal method is used when there is a large difference in the densities of ore and impurities.
   
   Ores of highly reactive metals are concentrated by chemical method.
   
   ROASTING, CALCINATION,SMELTING :
   Roasting is used to convert sulphide ores into oxides by heating for a longer period.
   
   
   
   Calcination is the process of heating the ore strongly in absence of air to remove (i) volatile impurities (ii)water [from hydrated ore] or (iii) to convert carbonate ore into metal oxide.
   
   
   
   Smelting is used to get an ore reduced to metal by heating whereby the metal is obtained in molten state.
   
   REDUCTION : The conversion of metal oxide into metal is called 'Reduction'. For chemical reduction, reducing agents like carbon, carbon monoxide and aluminium are used. Metals like zinc, iron, copper, nickel, tin and lead are obtained by chemical reduction of their oxides.
   

   Fe₂O_3(s) + 3C_(s) → 2Fe_(s) + 3CO_(g)
   
   3MnO₂ + 4Al → 3Mn + 2Al₂O₃
   

   
   
   The oxides of highly reactive metals cannot be reduced by chemical reduction using carbon or aluminium. Such metals are extracted by electrolytic reduction of their molten salts. During electrolysis the cathode acts as reducing agent by supplying electrons to metal ions. Sodium, potassium and aluminium are obtained by this method.
   
   REFINING OF METALS : The metals obtained from their ores after several metallurgical processes still contain some impurities. The removal of these impurities is called refining of metals. Refining is done mainly by two processes.
   
   
   
   1. LIQUATION (Liquefaction) method is used to remove impurities from metals like tin, lead and bismuth whose melting points are low as compared to those of impurities.
      
   2. ELECTROLYTIC REFINING is used to refine metals like zinc, lead, aluminium, copper, silver, gold, etc. The impure metal works as anode, a strip of pure metal is taken as cathode and a suitable salt of the metal to be purified in aqueous solution is taken as an electrolyte. The impure metal enters the solution from anode and then gets deposited on cathode. The impurities remain in the solution.
      
      In addition, the metals (in fact, metalloids) like silicon, germanium, etc. which are needed in ultrapure state for certain applications are obtained by zone refining method.
      
   
   
   
10. Write a note in detail : Refining of Metals by Electrochemical Method.
    
    ANS : Metals like zinc, lead, aluminium, copper, silver, gold, etc. are refined by this process.
    
    
    
    A rod of impure metal is taken as anode and a strip of pure metal is taken as cathode. an aqueous solution of a simple or complex salt of the metal to be purified is taken as electrolyte. On passing electric current at suitable voltage, pure metal is deposited at the cathode. The impurities either remain in the solution or collect at the bottom of the anode as 'Anode Mud'.
    
    For example, to obtain pure copper, impure copper rod is taken as anode, a strip of pure copper is taken as cathode and aqueous solution of copper sulphate is taken as the electrolyte.
    
    The reactions taking place at both the electrodes are :
    
    
    
    Crude copper contains very small amounts of iron, silver and gold. Iron dissolves in the solution whereas silver and gold collect at anode as anode mud and are obtained in the native state.
    
    
11. Describe Extraction of aluminium from bauxite.
    
    ANS :
    CONCENTRATION OF BAUXITE [BAYER'S PROCESS] :
    
    bauxite is concentrated by Bayer's process to obtain pure aluminium oxide (alumina).
    Bauxite is first roasted by heating to convert ferrous oxide into ferric oxide. The ore is then dried, powdered and treated with 45% aqueous solution of caustic soda (sodium hydroxide) and is heated to about160°C in a closed vessel for 6 to 8 hours at 5 to 6 atmospheric pressure. Sodium aluminate is formed.
    
    
    
    The insoluble impurities are filtered. Sodium aluminate is soluble in water and is obtained as filtrate. Sodium aluminate is then hydrolysed by adding excess water and constantly stirring it whereby gelatinous precipitates of aluminium hydroxide are obtained. To enhance the formation of Al(OH)₃, some Al(OH)₃ is added from outside as seedling.
    
    
    
    The precipitates of Al(OH)₃ are then washed repeatedly with water, dried and heated up to 1200°C.
    
    
    
    Thus, 99.5% pure alumina (Al₂O₃) is obtained.
    
    ELECTROLYSIS OF ALUMINIUM OXIDE [HALL-HAROULT PROCESS] :
    
    A special electrolytic cell invented by 'Hall' and 'Haroult' is used to reduce alumina to aluminium metal.
    
    
    
    Pure aluminium oxide is mixed with cryolite (Na₃AlF₆). The mixture is then melted in iron tank lined with carbon from inside. The carbon lining acts as cathode. The anode consists of a number of carbon rods which are dipped into the molten mass of Al₂O₃ and cryolite.
    
    When electric current is passed, aluminium metal is obtained at the cathode and oxygen gas gets liberated at anode. This oxygen gas reacts with carbon anode to form carbon dioxide. Due to this the carbon anode is gradually consumed.
    
    Molten aluminium metal being heavier than the electrolyte, is collected at the bottom of the tank.
    

    At Cathode
    
    2Al⁺³_(aq) + 6e^- → 2Al_(l)
    
    At Anode
    
    C_(s) + O^-2 → CO_(g) + 2e^-
    
    C_(s) + 2O^-2 → CO_2(g) + 4e^-
    

    
    
    
12. Describe extraction of iron using Blast Furnace.
    
    ANS : Blast furnace is used to obtain iron metal from haematite (Fe₂O₃). A proper mixture of haematite, coke and calcium carbonate is added to the blast furnace from the top and hot air is blown from the bottom of the blast furnace.
    
    
    
    [Diagram of blast furnace is only for information]
    
    
    
    1. At the bottom of the furnace coke burns in air to form carbon dioxide and large amount of heat is produced.
       

       C_(s) + O_2(g) → CO_2(g) + Heat

       
       
    2. In the center of the furnace carbon dioxide reacts with hot coke and forms carbon monoxide.
       

       CO_2(g) + C_(s) → 2CO_(g)
       

       
       
    3. In the upper part of the furnace the temperature is 400°C to 700°C. Here the reaction between iron oxide and carbon monoxide takes place in three stages and iron oxide is reduced to iron.
       

       3Fe₂O_3(s) + CO_(g) → 2Fe₃O_4(s) + CO_2(g)
       
       Fe₃O_4(s) + CO_(g) → 3FeO_(s) + CO_2(g)
       
       FeO_(s) + CO_(g) → Fe_(s) + CO_2(g)
       

       
       
    
    Due to large amount of heat produced in the furnace, limestone (CaCO₃) decomposes to calcium oxide. Calcium oxide reacts with sand (SiO₂) present as impurity in the ore and forms calcium silicate known as SLAG.
    

    CaO_(s) + SiO_2(s) → CaSiO_3(l)[slag]

    
    
    Both slag and iron ore are in molten state due to very high temperature in the lower part of the furnace. Both are collected separately from the bottom of the furnace. Once started, the blast furnace works for many months.
    
    
13. Mention physical properties of metals.
    
    ANS :
    
    
    
    • Metals have lustrous surface which can be polished.
      
    • Metals are solid (exception : gallium and mercury are in liquid state).
      
    • Metals are heavy (exception : sodium, potassium, magnesium and aluminium are comparatively lighter).
      
    • Metals are hard and cannot be cut with knife (exception : sodium, potassium and lead are soft and can be cut with knife).
      
    • Metals are good conductors of heat and electricity (exception : lead and mercury are bad conductors of heat).
      
    • Metals are ductile, i.e., they can be drawn in to wires.
      
    • Metals are malleable, i.e., they can be hammered and sheets can be prepared from them.
      
    • Metals have high melting points and boiling points. The melting point of iron is 1539°C.
      
    • Metals possess high tensile strength.
      
    • Most of the metals are sonorous, i.e., they produce sounding noise on collision.
      
    • Metals can be mixed with other metals and nonmetals to form alloys.
      
    
    
    
14. Write a note on chemical properties of metals OR Explain how metals react with oxygen, water, dilute acids, chlorine and hydrogen giving examples.
    
    ANS : Metals are electropositive elements since they have a tendency to lose electrons and form positively charged ions.
    
    REACTION WITH OXYGEN : Metals form oxides with oxygen. These oxides are basic in nature because when dissolved in water they form alkaline solutions. For example, sodium reacts with oxygen to give sodium oxide.
    

    4Na_(s) + O_2(g) → 2Na₂O_(s)

    
    
    Sodium oxide reacts with water to form sodium hydroxide ( an alkali).
    

    Na₂O_(s) + H₂O_(l) → 2NaOH_(aq)

    
    
    Oxides of metals like aluminium and zinc are called AMPHOTERIC OXIDES as they exhibit both acidic and basic behaviour.
    
    REACTION WITH WATER : Metals form either metal oxides or hydroxides when they react with water. Hydrogen gas is evolved in both cases.
    Highly reactive metals like sodium and potassium react violently with cold water.
    

    2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g)

    
    
    Magnesium reacts slowly with cold water but rapidly with hot boiling water.
    

    Mg_(s) + 2H₂O_(l) → Mg(OH)_2(aq) + H_2(g)

    
    
    Zinc and iron react with steam only (i.e., they do not react with cold or warm water).
    

    Zn_(s) + H₂O_(g) → ZnO_(s) + H_2(g)
    
    3Fe_(s) + 4H₂O_(g) → Fe₃O_4(s) + 4H_2(g)
    

    
    
    Less reactive metals like lead, copper, silver and gold do not react with water at all.
    
    REACTION WITH DILUTE ACIDS : Depending on their reactivity, metals react with dilute acids at different rates and liberate hydrogen gas.
    

    Mg_(s) + 2HCl_(aq) → MgCl_2(aq) + H_2(g)
    
    2Al_(s) + 6HCl_(aq) → 2AlCl_3(aq) + 3H_2(g)
    

    
    
    Copper does not react with dilute acids.
    
    REACTION WITH CHLORINE : Metals react with chlorine to form metal chlorides which are ionic compounds.
    

    2Na_(s) + Cl_2(g) → 2NaCl_(s)
    

    
    
    REACTION WITH HYDROGEN : All metals do not combine with hydrogen. Only reactive metals like sodium, potassium and calcium form their hydrides with hydrogen.
    

    2Na_(s) + H_2(g) → 2NaH_(s)
    
    Ca_(s) + H_2(g) → CaH_2(s)
    
    2K_(s) + H_2(g) → 2KH_(s)
    

    
    
    
15. Write a note on Corrosion.
    
    ANS :
    
    
    
    • Corrosion is a process in which rust is formed on metal surface when it is exposed to air, water or moisture. Oxygen of air, carbon dioxide and moisture(water) are mainly responsible for corrosion.
      
    • Some of the metals undergo corrosion. For example : (i) Green coloured salt is formed on copper and brass vessels.
      (ii) Iron becomes rusted because of its reaction with oxygen of air. Iron rust is mainly iron oxide (Fe₂O₃.xH₂O) which is red in colour.
      
    • Corrosion results in wastage of billions of rupees. Therefore, it is better to prevent corrosion.
    
    
    PREVENTION OF CORROSION :
    
    
    
    • Rusting of iron can be prevented by covering its surface with a paint. This method is less effective because rusting starts again if the paint is removed from some part.
      
    • Iron is galvanised by applying a thin layer of more active zinc on its surface. Zinc prevents rusting effectively. Even if a small amount of zinc is removed from the surface, rusting does not start again because zinc spreads to cover the surface and prevents corrosion.
      
    • To prevent corrosion of iron plates of steamers, blocks of more reactive metals like magnesium or zinc are combined with iron plates and then allowed to come in contact with seawater. Here iron plates act as cathode and magnesium(or zinc) act as anode because the oxidation potential of iron is less. The magnesium/zinc blocks get corroded in seawater so they are replaced periodically.
      
    • Corrosion can also be prevented by using suitable chemical inhibitors which form a chemical bond with the metal surface and prevent corrosion.
      
    • A layer of enamel applied on the metal can prevent corrosion.
      
    
    
    
16. Write a note on Alloys.
    
    ANS : An alloy is a homogeneous solid solution of two or more metals or a metal and a nonmetal. An alloy is generally prepared by heating the mixture of its constituents to molten state and then cooling it at room temperature. An alloy is prepared to obtain material with desired properties because the properties of constituents of an alloy are modified to some extent. Sometimes the melting point of an alloy is lower than that of the constituents. For example, solder is an alloy of lead and tin. Its melting point is lower than that of lead and tin and it is used in soldering of electrical wires. [Table to be posted]
    
    Pure gold cannot be used to make jewellery as it is very soft. To make it hard, it is generally alloyed with copper or silver. The purity of gold is expressed in CARATS. Pure gold is 24 carats. 18 carat gold means it contains 18 parts of gold in 24 parts by weight of the alloy.
    
    
17. Distinguish between metals and nonmetals based on physical properties.
    ANS :
    
    
    
18. Distinguish between metal and nonmetal based on chemical properties.
    
    ANS: