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Chemical Kinetics · Question 59

AIPMT 2007MCQMedium📈 Topic in 0% papers+4−1
1

The reaction of hydrogen and iodine monochloride is given as: H2(g) + 2ICl(g) 2HCl(g) + I2(g) This reaction is of first order with respect to H2(g) and ICl(g). The following mechanisms were proposed. Mechanism A: H2(g) + 2ICl(g) 2HCl(g) + I2(g) Mechanism B: H2(g) + ICl(g) HCl(g) + HI(g); slow HI(g) + ICl(g) HCl(g) + I2(g); fast Which of the above mechanism(s) can be consistent with the given information about the reaction?

  1. A and B both
  2. Neither A nor B
  3. A only
  4. B only

Answer

(4) B only

Solution

Observed rate law: Rate = k[H2][ICl] (first order in each).

Mechanism A is a single elementary step, so its rate law follows its stoichiometry:

Rate = k[H2][ICl]2 ⇒ second order in ICl, which does not agree.

Mechanism B: as per NCERT, the slowest step is the rate-determining step.

∴ Rate = k[H2][ICl] ⇒ first order in H2 and in ICl, which agrees.

Also, adding the two steps of B gives the overall reaction H2 + 2ICl 2HCl + I2.

∴ Only mechanism B is consistent.

Answer: (4)

AIPMT 2007

Keep practising — Chemical Kinetics

2

Consider the reaction : N2(g) + 3H2(g) 2NH3(g) The equality relationship between d[NH3]dt and - d[H2]dt is

  1. d[NH3]dt = - d[H2]dt
  2. d[NH3]dt = - 13 d[H2]dt
  3. + d[NH3]dt = - 23 d[H2]dt
  4. + d[NH3]dt = - 32 d[H2]dt
AIPMT 2006
3

For the reaction, 2A + B 3C + D, which of the following does not express the reaction rate?

  1. - d[A]2dt
  2. - d[C]3dt
  3. - d[B]dt
  4. d[D]dt
AIPMT 2006
4

The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is

  1. 2
  2. -2
  3. 1
  4. -1
AIPMT 2005
5

For a first order reaction A B the reaction rate at reactant concentration of 0.01 M is found to be 2.0 10-5 mol L-1 s-1. The half-life period of the reaction is

  1. 30 s
  2. 220 s
  3. 300 s
  4. 347 s
AIPMT 2005
6

The rate of a first order reaction is 1.5 10-2 mol L-1 min-1 at 0.5 M concentration of the reactant. The half-life of the reaction is

  1. 0.383 min
  2. 23.1 min
  3. 8.73 min
  4. 7.53 min
AIPMT 2004
7

The temperature dependence of rate constant (k) of a chemical reaction is written in terms of Arrhenius equation, k = A e-E*/RT. Activation energy (E*) of the reaction can be calculated by plotting

  1. k vs T
  2. k vs 1 T
  3. log k vs 1T
  4. log k vs 1 T
AIPMT 2003
8

If the rate of the reaction is equal to the rate constant, the order of the reaction is

  1. 0
  2. 1
  3. 2
  4. 3
AIPMT 2003
9

The reaction A B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B?

  1. 1 hour
  2. 0.5 hour
  3. 0.25 hour
  4. 2 hours
AIPMT 2003
10

The activation energy for a simple chemical reaction A B is Ea in forward direction. The activation energy for reverse reaction

  1. is negative of Ea
  2. is always less than Ea
  3. can be less than or more than Ea
  4. is always double of Ea
AIPMT 2003
11

The radioisotope, tritium (13H) has a half-life of 12.3 years. If the initial amount of tritium is 32 mg, how many milligrams of it would remain after 49.2 years?

  1. 1 mg
  2. 2 mg
  3. 4 mg
  4. 8 mg
AIPMT 2003

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