CBSE Class 12 Chemistry Short Questions & Answers

41 Which of the following statements about the catalyst is true?

A A catalyst accelerates the rate of reaction by bringing down the activation energy.

B A catalyst does not participate in reaction mechanism.

C A catalyst makes the reaction feasible by making ∆G more negative.

D A catalyst makes equilibrium constant more favourable for forward reaction.

View Answer

Answer: A catalyst accelerates the rate of reaction by bringing down the activation energy.

42 Which among the following is a false statement?

A For a first order reaction,

B Molecularity of a reaction may be zero or fraction.

C Rate of zero order reaction is independent of initial concentration of reactant.

D Half life of a third order reaction is inversely proportional to square of initial concentration of the reactant.

View Answer

Answer: Molecularity of a reaction may be zero or fraction.

43 What will be the fraction of molecules having energy equal to or greater than activation energy, Ea?

A e-Ea/Rt

B Ae-Ea/Rt

C A

D K

View Answer

Answer: e-Ea/Rt

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

A 11.3 h

B 1.8 h

C 12.1 h

D 9.7 h

View Answer

Answer: 11.3 h

45 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 Zero

B Half

C Two

D One

View Answer

Answer: Half

46 Activation energy of a chemical reaction can be determined by __________ .

A determining the rate constant at standard temperature.

B determining the rate constants at two temperatures.

C determining probability of collision.

D using catalyst.

View Answer

Answer: determining the rate constants at two temperatures.

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

A infinite

B 1.26 × 1015 s

C 2.52 × 1014 s

D 2.52 × 1028 s

View Answer

Answer: infinite

48 If cone, of reactant ‘A’ is increased 10 times and rate of reaction becomes 100 times. What is order with respect to ‘A’?

A -1

B 1

C 4

D 3

View Answer

Answer: 1

49 If the initial concentration of reactant is doubled, t1/2 is also doubled, the order of reaction is

A zero

B 3

C 2

D None of these

View Answer

Answer: zero

50 The rate of first order reaction is 0.04 mol L-1 s-1 at 10 sec. and 0.03 mol L-1 at 2C seconds after initiation of the reaction. t1/2 of reaction is

A 24.1 s

B 34.1 s

C 44.1 s

D 54.1 s

View Answer

Answer: 24.1 s

51 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 238.6 s

C 346.5 s

D 693.0 s

View Answer

Answer: 138.6 s

52 Which of the following is affected by catalyst?

A ∆H

B ∆S

C ∆G

D Ea

View Answer

Answer: Ea

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

A 0.5 × 10-3 s-1

B 5.0 × 10-3 s-1

C 5.0 × 10-2 s-1

D 0.5 × 10-2 s-1

View Answer

Answer: 0.5 × 10-3 s-1

54 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 0.72 M

B 3.60 M

C 1.08 M

D 0.36 M

View Answer

Answer: 0.72 M

55 The rate of first order reaction is 0.04 mol L-1 s-1 at 10 sec. and 0.03 mol L-1 at 2C seconds after initiation of the reaction. t1/2 of reaction is

A 24.1 s

B 34.1 s

C 44.1 s

D 54.1 s

View Answer