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Chemical Kinetics · Question 25

NEET (UG) 2019MCQEasy📈 Topic in 12% papers+4−1
1

For the chemical reaction N2(g) + 3H2(g) 2NH3(g) the correct option is :

  1. - d[N2]dt = 2 d[NH3]dt
  2. - d[N2]dt = 12 d[NH3]dt
  3. 3 d[H2]dt = 2 d[NH3]dt
  4. - 13 d[H2]dt = - 12 d[NH3]dt

Answer

(2) - d[N2]dt = 12 d[NH3]dt

Solution

As per NCERT, the rate of reaction is expressed by dividing the rate of change of concentration of each species by its stoichiometric coefficient (negative sign for reactants, positive for products):

Rate = - d[N2]dt = - 13 d[H2]dt = + 12 d[NH3]dt

- d[N2]dt = 12 d[NH3]dt

Option (4) has a wrong sign for NH3 and option (3) has wrong coefficients.

Answer: (2)

NEET (UG) 2019

Keep practising — Chemical Kinetics

2

The correct difference between first and second order reactions is that

  1. the rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations
  2. the half-life of a first-order reaction does not depend on [A]0; the half-life of a second order reaction does depend on [A]0
  3. a first-order reaction can be catalysed; a second-order reaction cannot be catalysed
  4. the rate of a first-order reaction does depend on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations
NEET 2018
3

When initial concentration of the reactant is doubled, the half-life period of a zero order reaction

  1. is halved
  2. is doubled
  3. is tripled
  4. remains unchanged.
NEET 2018
4

Mechanism of a hypothetical reaction X2 + Y2 2XY, is given below : (i) X2 X + X (fast) (ii) X + Y2 XY + Y (slow) (iii) X + Y XY (fast) The overall order of the reaction will be

  1. 2
  2. 0
  3. 1.5
  4. 1
NEET 2017
5

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

  1. 138.6 sec
  2. 346.5 sec
  3. 693.0 sec
  4. 238.6 sec
NEET 2017
6

The rate of first-order reaction is 0.04 mol L-1 s-1 at 10 seconds and 0.03 mol L-1 s-1 at 20 seconds after initiation of the reaction. The half-life period of the reaction is

  1. 44.1 s
  2. 54.1 s
  3. 24.1 s
  4. 34.1 s
NEET 2016 (Phase 1)
7

The addition of a catalyst during a chemical reaction alters which of the following quantities?

  1. Enthalpy
  2. Activation energy
  3. Entropy
  4. Internal energy
NEET 2016 (Phase 1)
8

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.
NEET 2016 (Phase 2)
9

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
10

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)
11

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)

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