12th Chemistry chapter 4: full solution, notes, MCQ, & free PDF | Bihar board

1.  When a chemical reaction takes place, during the course of the reaction the rate of reaction

• • (a) keeps on increasing with time
  • (b) remains constant with time
  • (c) keeps on decreasing with time
  • (d) shows irregular trend with time

Ans (C)

2. The rate of disappearance of SO₂in the reaction, 2SO₂ + O₂ → 2SO₃ is 1.28 x 10^-5 M s^-1. The rate of appearance of SO₃ is …………..

• • (a) 64 x 10^-5 M s^-1
  • (b) 0.32 x 10^-5 M s^-1
  • (c) 2.56 x 10^-5 Ms^-1
  • (d) 1.28 x 10^-5 M s^-1

Ans (D)

3. In a reaction 2X → Y, the concentration of X decreases from 3.0 moles/litre to 2.0 moles/litre in 5 minutes. The rate of reaction is ………………..

• • (a) 1 mol L^-1 min^-1
  • (b) 5 mol L^-1 min^-1
  • (c) 1 mol L^-1 min^-1
  • (d) 0.5 mol L^-1 min^-1

Ans (A)

4. The rate constant of a reaction depends upon

• • (a) temperature of the reaction
  • (b) extent of the reaction
  • (c) initial concentration of the reaction
  • (d) the time of completion of reaction

Ans (A)

5. Rate constant in case of first order reaction is

• • (a) inversely proportional to the concentration units
  • (b) independent of concentration units
  • (c) directly proportional to concentration units
  • (d) inversely proportional to the square of concentration units

Ans (B)

6. The rate constant for the reaction, 2N₂O₂→ 4NO₂ + O₂ is 2 x 10^–5s^-1. If rate of reaction is 1.4 x 10^-5 mol L^-1 s^-1, what will be the concentration of N₂O₅ in mol L^-1?

• • (a) 8
  • (b) 0.7
  • (c) 1.2
  • (d) 1

Ans (B)

7. The order of reaction is decided by…………..

• • (a) temperature
  • (b) mechanism of reaction as well as relative concentration of reactants
  • (c) molecularity
  • (d) pressure

Ans (B)

8. Which of the following is an example of a fraction order reaction ?

• • (a) NH₄NO₂ → N₂ +2H₂O
  • (b) NO + O₃ → NO₂+O₂
  • (c) 2NO + Br₂ → 2NOBr
  • (d) CH₃CHO → CH₄ + CO

Ans (D)

9. What will be the rate equation for the reaction 2X + Y→ Z, if the order of the reaction is zero ?

• • (a) Rate = k[X] [Y]
  • (b) Rate = k
  • (c) Rate = A[X]⁰[Y]
  • (d) Rate = k[X][Y]⁰

Ans (B)

10. The unit of rate constant for the reaction, 2H₂+ 2NO → 2H₂O + N₂which has rate – k[H₂][NO]², is …………..

• • (a) molL^–1s^-1
  • (b) s^-1
  • (c) mol^–1L²s^-1
  • (d) mol L^-1

Ans (C)

12th chemistry chapter 4 most mcq solution

11. The unit of rate and rate constant are same for a…………….

• • (a) zero order reaction
  • (b) first order reaction
  • (c) second order reaction
  • (d) third order reaction

Ans (A)

12. The number of molecules of the reactants taking part in a single step of the reaction is indicative of

• • (a) order of a reaction
  • (b) molecularity of a reaction
  • (c) fast step of the mechanism of a reaction
  • (d) half-life of the reaction

Ans (B)

13. The overall rate of a reaction is governed by

• • (a) the rate of fastest intermediate step
  • (b) the sum of the rates of all intermediate steps
  • (c) the average of the rates of all the intermediate steps
  • (d) the rate of slowest intermediate step.

Ans (D)

14. Radioactive disintegration is an example of ……………

• • (a) zero order reaction
  • (b) first order reaction
  • (c) second order reaction
  • (d) third order reaction

Ans (B)

15. A first order reaction has a rate constant 1.15 x 10^-3s^-1. How long will 5 g of this reaction take to reduce to 3 g ?

• • (a) 444 s
  • (b) 400 s
  • (c) 528 s
  • (d) 669 s

Ans (A)

16. Half-life period of a first order reaction is 10 min. What percentage of the reaction will be completed in 100 min ?

• • (a) 25%
  • (b) 50%
  • (c) 99.9%
  • (d) 75%

Ans (C)

17. The rate constant for a first order reaction is 2 x 10^-2min^-1. The half-life period of reaction is

• • (a) 69.3 min
  • (b) 34.65 min
  • (c) 17.37 min
  • (d) 3.46 min

Ans (B)

18. The value of rate of a pseudo first order reaction depends upon

• • (a) the concentration of both the reactants present in the reaction
  • (b) the concentration of the reactant present in small amount
  • (c) the concentration of the reactant present in excess
  • (d) the value of ΔH of the reaction

Ans (B)

19. Under what conditions a bi-molecular reaction may be kinetically of first order ?

• • (a) When both reactants have same concentration
  • (b) When one of the reacting species is in large excess
  • (c) When the reaction is at equilibrium
  • (d) When the activation energy of reaction is less

Ans (B)

20. For an endothermic reaction, AH represents the enthalpy of the reaction in kj mol^-1. The minimum amount of activation energy will be

• • (a) less than zero
  • (b) equal to ΔH
  • (c) less than ΔH
  • (d) more than ΔH

Ans (D)

Bihar Board most important notes 12th chemistry chapter 4

21. The decomposition of a hydrocarbon follows the equation k = (4.5 x 10¹¹ s^-1) e^-28000K/T. What will be the value of activation energy ?

• • (a) 669 kJ mol^-1
  • (b) 232.79   kJ mol^-1
  • (c) 4.5 x 10^-1 kJ mol^-1
  • (d) 28000 kJ mol^-1

Ans (B)

22. The rate constant is given by the equation k = P.Ze^-Ea/RT Which factor should register a decrease for the reaction to proceed more rapidly ?

• • (a) T
  • (b) Z
  • (c) E
  • (d) P

Ans (C)

23. Threshold energy is equal to ……………

• • (a) activation energy
  • (b) activation energy – energy of molecules
  • (c) activation energy + energy of molecules
  • (d) None of these

Ans (C)

24. The role of a catalyst is to change………………..

• • (a) Gibbs energy of reaction
  • (b) enthalpy of reaction
  • (c) activation energy of reaction
  • (d) equilibrium constant

Ans (C)

25. In the presence of a catalyst, the heat evolved or absorbed during the reaction…………..

• • (a) increases
  • (b) decreases
  • (c) remains unchanged
  • (d) may increase or decrease

Ans (C)

26. A first order reaction is 50% completed in 1.26 x 10¹⁴How much time would it take for 100% completion ?

• • (a) 1.26 x 10¹⁵ s
  • (b) 2.52 x 10¹⁴ s
  • (c) 2.52 x 10²⁸ s
  • (d) Infinite

Ans (D)

27. The half life period of first order reaction is 1386 seconds. The specific rate constant of the reaction is

• • (a) 0.5 × 10^-2 s^-1
  • (b) 0.5 × 10^-3 s^-1
  • (c) 5.0 × 10^-2 s^-1
  • (d) 5.0 × 10^-3 s^-1

Ans (B)

28. The rate constant of a reaction A → B is 0.6 × 10³ mole per second. If the concentration of [A] is 5 M, then what will be concentration of [B] after 20 months?

• • (a) 0.36 M
  • (b) 0.72 M
  • (c) 1.08 M
  • (d) 3.60 M

Ans (B)

29. Which of the following is affected by catalyst?

• • (a) ∆H
  • (b) ∆S
  • (c) ∆G
  • (d) Ea

Ans (D)

30. A first order reaction has specific reaction rate 10^-2s^-1. How much time it will take for 20g of reactant to reduce to 5g?

• • (a) 138.6 s
  • (b) 346.5 s
  • (c) 693.0 s
  • (d) 238.6 s

Ans (A)

BSEB 12th chemistry chapter 4 most objective solution

31. For a chemical reaction A→B, it is found that the rate of reaction doubles when the concentration of A is increased four times. The order of reaction is

• • (a) Two
  • (b) One
  • (c) Half
  • (d) Zero

Ans (C)

32. The half life of the first order reaction having rate constant K = 1.7 x 10^-5s^-1is

• • (a) 12.1 h
  • (b) 9.7 h
  • (c) 11.3 h
  • (d) 1.8 h

Ans (C)

33. The rate constant of a reaction depends upon : 

• • (a) temperature of the reaction
  • (b) extent of the reaction
  • (c) initial concentration of the reactants
  • (d) the time of completion of reaction

Ans (D)

34. The unit of rate and rate constant are same for a : 

• • (a) zero order reaction
  • (b) first order reaction
  • (c) second order reaction
  • (d) third order reaction

Ans (A)

35. For a unimolecular reaction : 

• • (a) the order and molecularity of the slowest step are equal to one
  • (b) molecularity of the reaction can be zero, one or two
  • (c) more than one reacting species are involved in one step
  • (d) molecularity of the reaction can be determined only experimentally

Ans (A)

36. The overall rate of a reaction is governed by 

• • (a) the rate of fastest intermediate step
  • (b) the sum total of the rates of all intermediate steps.
  • (c) the average of the rates of all the intermediate steps
  • (d) the rate of slowest intermediate step

Ans (D)

37. H₂(g) + Cl₂(g) → 2 HCI (g). The order of this reaction is : 

• • (a) Zero order
  • (b) First order
  • (c) Second order
  • (d) None of these

Ans (A)

38. For a reaction if activation energies for forward and backward reactions are the same, then :

• • (a) ΔH = 0
  • (b) ΔS = 0
  • (c) The order is zero
  • (d) None of these

Ans (A)

39. Radioactive disintegration is an example of : 

• • (a) zero order reaction
  • (b) first order reaction
  • (c) second order reaction
  • (d) third order reaction

Ans (B)

40. t_1/2for first order reaction is : 

• • (a) 0.6 / k
  • (b) 0.693 / k
  • (c) 0.683 / k
  • (d) 0.10 / k

Ans (B)

41. The rate at which a substance reacts, depends upon its 

• • (a) Atomic Mass
  • (b) Equivalent Mass
  • (c) Molecular Mass
  • (d) Active Mass

Ans (D)

42. Half life period of first order reaction is independent of : 

• • (a) Initial concentration of reactant
  • (b) Temperature
  • (c) Pressure
  • (d) None of these

Ans (B)

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