RATE OF REACTION-CHEMICAL EQUILIBRIUM-I :MCQs & SHORT ANSWERS

*INDEX-TOPIC SEARCH

MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

1. Formation of petroleum in earth's crust is a ______ reaction.
   
   
   
   1. geochemical
   2. biochemical
   3. physiochemical
   4. physical
      
   
   
2. During a chemical reaction the concentration of reactants ______.
   
   
   
   1. does not change
   2. increases
   3. decreases
   4. may increase
      
   
   
3. Chemical equilibrium establishes if a reaction takes place in ______.
   
   
   
   1. a closed system
   2. an open system
   3. gaseous state
   4. liquid state
      
   
   
4. The decrease in concentration of reactants ______ as the increase in the concentration of products.
   
   
   
   1. may be the same
   2. is the same
   3. is not the same
   4. may not be the same
      
   
   
5. In the manufacture of ammonia ______ is used as catalyst.
   
   
   
   1. chlorine
   2. oxygen
   3. iron
   4. mercury
      
   
   
6. ______ suggested a theory based on the transfer of electron pair for defining acid and base.
   
   
   
   1. Arrhenius
   2. Bronsted
   3. Lowry
   4. Lewis
      
   
   
7. ______ defined p^H in 1909.
   
   
   
   1. Arrhenius
   2. Sorensen
   3. Lewis
   4. Haber
      
   
   
8. Hydrogen ion concentration is equal to hydroxyl ion concentration in ______.
   
   
   
   1. neutral water
   2. sodium hydroxide
   3. hydrogen chloride
   4. CH₃COOH
      
   
   
9. The concentration of H⁺ ion in neutral water is ______.
   
   
   
   1. 1 x 10^-7 mol/litre
   2. -7.0 mol/litre
   3. 7.0 mol/litre
   4. 1/7 mol/litre
      
   
   
10. The p^H of an acidic solution is ______.
    
    
    
    1. 7
    2. more than 7
    3. less than 7
    4. negative
       
    
    
11. The p^H of a basic solution is ______.
    
    
    
    1. 7
    2. more than 7
    3. less than 7
    4. negative
       
    
    
12. A solution is neutral when its p^H is ______.
    
    
    
    1. 0
    2. 7
    3. -7
    4. 10^-7
       
    
    
13. What type of reaction is the production of ammonia by chemical reaction between hydrogen and nitrogen ?
    
    
    
    1. Slow reaction
    2. Fast reaction
    3. Very slow reaction
    4. Very fast reaction
       
    
    
14. What is the unit of the rate of a reaction ?
    
    
    
    1. Molar
    2. Second
    3. molar/second
    4. mole/second
       
    
    
15. Which ion from the following is released from an acid according to Arrhenius' theory ?
    
    
    
    1. H⁺
    2. OH^-
    3. N^-
    4. O^-2
       
    
    
16. In p^H scale the base of the logarithm of molar concentration of H₃O⁺ is ______.
    
    
    
    1. 10
    2. 20
    3. 50
    4. 100
       
    
    
17. What will be the value of the p^H of the blood ?
    
    
    
    1. less than 7
    2. greater than 7
    3. equal to 7
    4. 0
       
    
    
18. The change of ice to water is...
    
    
    
    1. a physical change
    2. a chemical change
    3. both physical and chemical change
    4. neither physical nor chemical change
       
    
    
19. Conversion of milk into curd is...
    
    
    
    1. a physical change
    2. a chemical change
    3. not a chemical change
    4. neither physical nor chemical change
       
    
    
20. Preparation of vegetable ghee from vegetable oil is______ reaction.
    
    
    
    1. chlorination
    2. sulphonation
    3. hydrogenation
    4. hydrolysis
       
    
    
21. The reaction between an acid and a base is______ reaction.
    
    
    
    1. chlorination
    2. hydrolysis
    3. neutralisation
    4. hydrogenation
       
    
    
22. The acid-base theory by Lowry and Bronsted...
    
    
    
    1. is based on donation of electron pair.
    2. does not give importance to solvent.
    3. gives importance to solvent.
    4. gives operational definition of acid and base.
       
    
    
23. The acid-base theory of Lewis...
    
    
    
    1. is based on proton transfer.
    2. gives operational definition of acid and base.
    3. is based on theory of ionisation.
    4. is based on transfer of electron pair.
       
    
    
24. p^H + p^OH = ______.
    
    
    
    1. 0
    2. 7
    3. 14
    4. between 0 and 7
       
    
    

ANSWERS TO MCQs:

(1) A (2) C (3) A (4) B (5) C (6) D (7) B (8) A (9) A (10) C (11) B (12) B (13) B (14) C (15) A (16) A (17) B (18) A (19) B (20) C (21) C (22) C (23) D (24) C

SHORT QUESTIONS

ANSWER IN SHORT:

1. What happens when a piece of metal zinc is added to the aqueous solution of hydrochloric acid ?
   
        ANS :Zinc chloride (ZnCl₂) and hydrogen gas are produced.


2. Define : Slow reaction.
   
        ANS :A reaction which takes longer time to complete is called SLOW REACTION.


3. Give two examples of slow reactions.
   
        ANS :Rusting of iron and digestion of food are two examples of slow reaction.[Also, the formation of petroleum in earth's crust].


4. Define : Fast reaction.
   
        ANS :A reaction which takes very short duration for completion is called fast reaction.


5. What happens when pure magnesium wire is heated ?
   
        ANS :When pure magnesium wire is heated it catches fire, burns with a flash and forms magnesium oxide in a few seconds.


6. Give two examples of reactions taking place in closed system.
   
        ANS :Manufacture of ammonia by Haber's process and preparation of vegetable ghee are examples of reactions occurring in closed system.


7. Give two examples of fast reactions.
   
        ANS :Heating of magnesium in open air, preparation of ammonia by Haber's process ( and combustion of fuels like petrol, diesel, etc.) are fast reactions.


8. What is an irreversible reaction ?
   
        ANS :If in a reaction the products formed do not combine back to form original reactants under the same set of conditions, then the reaction is called IRREVERSIBLE REACTION.


9. Give examples of irreversible reaction.
   
        ANS :Combustion of methane, combustion of petrol, burning of magnesium wire, all geochemical reactions, etc. are irreversible reactions.


10. What is a reversible reaction ?
    
         ANS :Under the same set of reaction conditions, if the products formed during a reaction recombine to form original reactants then the reaction is called a REVERSIBLE REACTION.


11. Give examples of reversible reaction.
    
         ANS :Preparation of ammonia by Haber's process and decomposition of calcium carbonate in a closed vessel are reversible reactions.


12. Write the reaction for the preparation of ammonia by Haber's process.
    
         ANS :
    

    
    700K
    200atm
    iron oxide
    N_2(g) + 3H_2(g)     ↔      2NH_3(g) + Heat
    



13. What do we mean by forward and reverse reaction ?
    
         ANS :The reaction in which the reactants react to form products is called FORWARD REACTION and with the same set of conditions if the products combine to form original reactants, then that reaction is called REVERSE REACTION.


14. What does the rate of a chemical reaction indicate ?
    
         ANS :The rate of a chemical reaction indicates how fast the reaction takes place, how much of the reactants is consumed and how much of the products is formed during given time.


15. Define : Rate of reaction.
    
         ANS :The decrease in the concentration of reactants or the increase in the concentration of products per unit time during a chemical reaction is called the RATE OF THAT REACTION.


16. How (in what units) is the change in the concentration of reactants/products expressed ?
    
         ANS :The change in the concentration of a reactant/product in a reaction is expressed in mole/litre or mole-litre^-1.


17. Define : Molarity.
    
         ANS :The number of gram moles of a substance present in 1 litre of solution is known as molarity.


18. What is 1 molar (1 M) solution ?
    
         ANS :1 molar solution of a substance is a solution that contains 1 gram mole of that substance dissolved in 1 litre solution.


19. What is the equilibrium state ?
    
         ANS :When the rate of conversion of reactants into products is equal to the rate of conversion of products into reactants in a reaction, the reaction is said to be in equilibrium state.
    OR
    If two parameters are acting against each other with same rate in a system, then the system is said to be in equilibrium state.


20. What is physical equilibrium ?
    
         ANS :In equilibrium state when there is change only in physical state of the reactants and products without any change in their chemical form, the state of equilibrium is called physical equilibrium.


21. What is chemical equilibrium ?
    
         ANS :If during equilibrium state the reactants and products undergo a chemical change with or without a change in their physical state, the state of equilibrium is called chemical equilibrium.


22. Write the formula of ethylacetate.
    
         ANS :The formula of ethylacetate is CH₃COOC₂H₅ OR CH₃COOCH₂CH₃.


23. State the Law of Chemical Equilibrium.
    
         ANS :At a given temperature, the product of concentration of reaction products each raised to the respective stoichiometric coefficient in the balanced chemical equation divided by the product of concentration of reactants raised to their respective stoichiometric coefficient has a constant value.


24. What was the concept of acid-base theory proposed by Arrhenius ?
    
         ANS :According to Arrhenius, acids are the substances that produce H⁺ ions and bases are the substances that produce OH^- ions on ionisation.


25. Who proposed 'Proton-Transfer Theory' for acid and base ?
    
         ANS :Bronsted and Lowry proposed 'Proton-Transfer Theory' for acid and base.


26. Define : p^H
    
         ANS :p^H (of a solution) is the negative logarithm of the hydrogen ion concentration (in moles/litre) to the base 10.


27. What is an exothermic reaction ?
    
         ANS :A chemical reaction in which heat is released is called an exothermic reaction.


28. What is an endothermic reaction ?
    
         ANS :A chemical reaction in which heat is absorbed is called an endothermic reaction.


29. The preparation of ammonia by Haber's process is an exothermic reaction. True or false ?
    
         ANS :This is a true statement.


30. Write the p^H value of pure water at 25°C.
    
         ANS :The p^H value of pure water at 25°C. is 7.0.


31. Who suggested the p^H scale and when ?
    
         ANS :Sorensen suggested the p^H scale in 1909 AD.


32. State the Law of Mass-Action (Guldberg-Waage Law).
    
         ANS :At constant temperature, the reaction rate of a substance is directly proportional to its active mass and the overall rate of a chemical reaction is directly proportional to the product of the active masses of the reactants. [Note : Active mass means molar concentration]


33. What type of p^H value will blood, urine and lemon juice have ?
    
         ANS :Blood is basic. Its p^H will be more than 7.0 whereas both urine and lemon juice will have p^H less than 7.0 as they are acids.


34. Which acid is present in the stomach of human being ?
    
         ANS :Hydrochloric acid (gastric juice) is present in the stomach of human being.


35. What is the difference between combustion of coal and that of LPG ?
    
         ANS :Combustion of coal is relatively a slow reaction and that of LPG is a fast reaction.


36. What is used as a catalyst in preparation of vegetable ghee ?
    
         ANS :Nickel is used as the catalyst in the preparation of vegetable ghee.


37. Why are the definitions of acid and base by Robert Boyle called 'operational' type definition ?
    
         ANS :Robert Boyle's definitions of acid and base are called 'operational' type definitions because they are based on properties.


38. In pure water the concentration of H⁺ and OH^- ions is equal(same). True or false ?
    
         ANS :It is a true statement.