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Chemical Kinetics · Question 32

NEET 2016 (Phase 2)MCQMedium📈 Topic in 38% papers+4−1
1

The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the

  1. rate is proportional to the surface coverage
  2. rate is inversely proportional to the surface coverage
  3. rate is independent of the surface coverage
  4. rate of decomposition is very slow.

Answer

(1) rate is proportional to the surface coverage

Solution

In a surface-catalysed decomposition, rate ∝ fraction of the surface covered by the gas.

At low pressure the surface coverage is small and is proportional to the pressure (concentration) of PH3:

Rate ∝ surface coverage ∝ pPH3 first order.

(At high pressure the surface is fully covered and the rate becomes independent of pressure, i.e. zero order.)

Answer: (1)

NEET 2016 (Phase 2)

Keep practising — Chemical Kinetics

2

The rate constant of the reaction A B is 0.6 10-3 mol L-1 s-1. If the concentration of A is 5 M, then concentration of B after 20 minutes is

  1. 3.60 M
  2. 0.36 M
  3. 0.72 M
  4. 1.08 M
AIPMT 2015
3

The activation energy of a reaction can be determined from the slope of which of the following graphs?

  1. k vs. 1T
  2. T k vs. 1T
  3. k vs. T
  4. kT vs. T
AIPMT 2015 (Cancelled)
4

When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is

  1. second
  2. more than zero but less than first
  3. zero
  4. first.
AIPMT 2015 (Cancelled)
5

A reaction having equal energies of activation for forward and reverse reactions has

  1. H = 0
  2. H = G = S = 0
  3. S = 0
  4. G = 0
NEET 2013
6

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 C to 35 C? (R = 8.314 J mol-1 K-1)

  1. 34.7 kJ mol-1
  2. 15.1 kJ mol-1
  3. 342 kJ mol-1
  4. 269 kJ mol-1
NEET 2013
7

For a reaction between A and B the order with respect to A is 2 and the order with respect to B is 3. The concentrations of both A and B are doubled, the rate will increase by a factor of

  1. 12
  2. 16
  3. 32
  4. 10
NEET 2013 (Karnataka)
8

A reaction is 50\% complete in 2 hours and 75\% complete in 4 hours. The order of reaction is

  1. 1
  2. 2
  3. 3
  4. 0
NEET 2013 (Karnataka)
9

Activation energy (Ea) and rate constants (k1 and k2) of a chemical reaction at two different temperatures (T1 and T2) are related by

  1. k2k1 = - EaR ( 1T1 - 1T2 )
  2. k2k1 = - EaR ( 1T2 - 1T1 )
  3. k2k1 = - EaR ( 1T2 + 1T1 )
  4. k2k1 = EaR ( 1T1 - 1T2 )
AIPMT 2012 (Mains)
10

In a reaction, A + B product, rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentrations of both the reactants (A and B) are doubled, rate law for the reaction can be written as

  1. rate = k[A][B]2
  2. rate = k[A]2[B]2
  3. rate = k[A][B]
  4. rate = k[A]2[B]
AIPMT 2012 (Prelims)
11

In a zero-order reaction, for every 10 rise of temperature, the rate is doubled. If the temperature is increased from 10 to 100 , the rate of the reaction will become

  1. 256 times
  2. 512 times
  3. 64 times
  4. 128 times
AIPMT 2012 (Prelims)

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