Chemical Kinetics Practice Test — Class 12 Chemistry

12th Standard Chemistry — Chemical Kinetics: Online Practice Test

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For a first order reaction \(A \rightarrow B\) the rate constant is \(x\) \(min^{-1}\). If the initial concentration of A is \(0.01M\), the concentration of A after one hour is given by the expression.

A.\(0.01 e^{-x}\) B.\(1 \times 10^{-2} (e^{-60})^{-x}\) C.\(1 \times 10^{-2} e^{-60x}\) D.none of these

A zero order reaction \(X \rightarrow Product\), with an initial concentration \(0.02M\) has a half life of \(10 min\). if one starts with concentration \(0.04M\), then the half life is

A.10 s B.5 min C.20 min D.cannot be predicted using the given information

For a first order reaction \(A \rightarrow product\) with initial concentration \(x\) \(mol L^{-1}\), has a half life period of 2.5 hours. For the same reaction with initial concentration \(\frac{x}{2}\) \(mol L^{-1}\) the half life is

A.\(2.5 \times 2\) hours B.\(2.5 / 2\) hours C.2.5 hours D.Without knowing the rate constant, \(t_{1/2}\) cannot be determined from the given data

For the reaction, \(2NH_3 \rightarrow N_2 + 3H_2\), if \(-\frac{d[NH_3]}{dt} = k_1[NH_3]\), \(\frac{d[N_2]}{dt} = k_2[NH_3]\), \(\frac{d[H_2]}{dt} = k_3[NH_3]\) then the relation between \(k_1, k_2\) and \(k_3\) is

A.\(k_1 = k_2 = k_3\) B.\(k_1 = 3k_2 = 2k_3\) C.\(1.5k_1 = 3k_2 = k_3\) D.\(2k_1 = k_2 = 3k_3\)

The decomposition of phosphine (\(PH_3\)) on tungsten at low pressure is a first order reaction. It is because the (NEET)

A.rate is proportional to the surface coverage B.rate is inversely proportional to the surface coverage C.rate is independent of the surface coverage D.rate of decomposition is slow

For a reaction \(Rate = k[acetone]^{3/2}\) then unit of rate constant and rate of reaction respectively is

A.\(mol L^{-1} s^{-1}, mol^{-1/2} L^{1/2} s^{-1}\) B.\(mol^{-1/2} L^{1/2} s^{-1}, mol L^{-1} s^{-1}\) C.\(mol^{1/2} L^{-1/2} s^{-1}, mol L^{-1} s^{-1}\) D.\(mol L s^{-1}, mol^{1/2} L s^{-1}\)

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

A.Enthalpy B.Activation energy C.Entropy D.Internal energy

Consider the following statements: (i) increase in concentration of the reactant increases the rate of a zero order reaction. (ii) rate constant k is equal to collision frequency A if \(E_a = 0\) (iii) rate constant k is equal to collision frequency A if \(E_a = \infty\) (iv) a plot of ln k vs T is a straight line. (v) a plot of ln k vs 1/T is a straight line with a positive slope. Correct statements are

A.(ii) only B.(ii) and (iv) C.(ii) and (v) D.(i), (ii) and (v)

In a reversible reaction, the enthalpy change and the activation energy in the forward direction are respectively \(-x kJ mol^{-1}\) and \(y kJ mol^{-1}\). Therefore, the energy of activation in the backward direction is

A.\((y-x) kJ mol^{-1}\) B.\((x+y) J mol^{-1}\) C.\((x-y) kJ mol^{-1}\) D.\((x+y) \times 10^3 J mol^{-1}\)

Q10

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK\(^{-1}\)mol\(^{-1}\))

A.234.65 kJ mol\(^{-1}\) K\(^{-1}\) B.434.65 kJ mol\(^{-1}\) K\(^{-1}\) C.2.305 kJ mol\(^{-1}\) D.334.65 J mol\(^{-1}\) K\(^{-1}\)

Q11

This reaction follows first order kinetics. The rate constant at particular temperature is \(2.303 \times 10^{-2}\) hour\(^{-1}\). The initial concentration of cyclopropane is 0.25 M. What will be the concentration of cyclopropane after 1806 minutes?

A.0.125M B.0.215M C.0.25 \times 2.303M D.0.05M

Q12

For a first order reaction, the rate constant is 6.909 min\(^{-1}\). The time taken for 75% conversion in minutes is

A.\(\frac{3}{2} \log 2\) B.\(\frac{2}{3} \log 2\) C.\(\frac{3}{2} \log \frac{3}{4}\) D.\(\frac{2}{3} \log \frac{4}{3}\)

Q13

In a first order reaction x \(\rightarrow\) y ; if k is the rate constant and the initial concentration of the reactant x is 0.1M, then, the half life is

A.\(\frac{\log 2}{k}\) B.\(\frac{0.693(0.1)}{k}\) C.\(\frac{\ln 2}{k}\) D.none of these

Q14

Predict the rate law of the following reaction based on the data given below: 2A + B \(\rightarrow\) C + 3D | Reaction | [A] (min) | [B] (min) | Rate (M s\(^{-1}\)) | | :--- | :--- | :--- | :--- | | 1 | 0.1 | 0.1 | x | | 2 | 0.2 | 0.1 | 2x | | 3 | 0.1 | 0.2 | 4x | | 4 | 0.2 | 0.2 | 8x |

A.rate = k[A]\(^2\)[B] B.rate = k[A][B]\(^2\) C.rate = k[A][B] D.rate = k[A]\(^{1/2}\)[B]\(^{3/2}\)

Q15

The rate constant of a reaction is \(5.8 \times 10^{-2}\) s\(^{-1}\). The order of the reaction is

A.First order B.zero order C.Second order D.Third order

Q16

For the reaction N\(_2\)O\(_5\)(g) \(\rightarrow\) 2NO\(_2\)(g) + 1/2 O\(_2\)(g), the value of rate of disappearance of N\(_2\)O\(_5\) is given as \(6.5 \times 10^{-2}\) mol L\(^{-1}\) s\(^{-1}\). The rate of formation of NO\(_2\) and O\(_2\) is given respectively as

A.\(3.25 \times 10^{-2}\) mol L\(^{-1}\) s\(^{-1}\) and \(1.3 \times 10^{-1}\) mol L\(^{-1}\) s\(^{-1}\) B.\(1.3 \times 10^{-2}\) mol L\(^{-1}\) s\(^{-1}\) and \(3.25 \times 10^{-2}\) mol L\(^{-1}\) s\(^{-1}\) C.\(1.3 \times 10^{-1}\) mol L\(^{-1}\) s\(^{-1}\) and \(3.25 \times 10^{-2}\) mol L\(^{-1}\) s\(^{-1}\) D.None of these

Q17

During the decomposition of H\(_2\)O\(_2\) to give dioxygen, 48 g O\(_2\) is formed per minute at certain point of time. The rate of formation of water at this point is

A.0.75 mol min\(^{-1}\) B.1.5 mol min\(^{-1}\) C.2.25 mol min\(^{-1}\) D.3.0 mol min\(^{-1}\)

Q18

If the initial concentration of the reactant is doubled, the time for half reaction is also doubled. Then the order of the reaction is

A.Zero B.one C.Fraction D.none

Q19

In a homogeneous reaction A \(\rightarrow\) B + C + D, the initial pressure was P\(_0\) and after time t it was P. expression for rate constant in terms of P\(_0\), P and t will be

A.\(k = \frac{2.303}{t} \log \frac{2P_0}{3P_0 - P}\) B.\(k = \frac{2.303}{t} \log \frac{2P_0}{P_0 - P}\) C.\(k = \frac{2.303}{t} \log \frac{3P_0 - P}{2P_0}\) D.\(k = \frac{2.303}{t} \log \frac{2P_0}{3P_0 - P^2}\)

Q20

If 75% of a first order reaction was completed in 60 minutes, 50% of the same reaction under the same conditions would be completed in

A.20 minutes B.30 minutes C.35 minutes D.75 minutes

Q21

The half life period of a radioactive element is 140 days. After 560 days, 1 g of element will be reduced to

A.\(\frac{1}{2}\) g B.\(\frac{1}{4}\) g C.\(\frac{1}{8}\) g D.\(\frac{1}{16}\) g

Q22

The correct difference between first and second order reactions is that (NEET)

A.A first order reaction can be catalysed; a second order reaction cannot be catalysed. B.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\(_0\)]. C.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. D.The rate of a first order reaction is independent of temperature jumps.

Q23

If a first order reaction is 93.75% complete in 2 hours, the half life of the reaction is

A.15 minutes B.45 minutes C.30 minutes D.60 minutes

Q24

Which of the following units is used to express the rate of a gas phase reaction when the concentration of species is expressed in terms of partial pressure?

A.mol L\(^{-1}\) s\(^{-1}\) B.atm s\(^{-1}\) C.mol s\(^{-1}\) D.atm mol\(^{-1}\) s\(^{-1}\)

Q25

For a general reaction \(x A + y B \to l C + m D\), what is the correct relationship between the rates of change of concentration for the different species?

A.Rate = \(-x \frac{d[A]}{dt} = -y \frac{d[B]}{dt}\) B.Rate = \(-\frac{1}{x} \frac{d[A]}{dt} = \frac{1}{l} \frac{d[C]}{dt}\) C.Rate = \(\frac{1}{y} \frac{d[B]}{dt} = \frac{1}{m} \frac{d[D]}{dt}\) D.Rate = \(-x \frac{d[A]}{dt} = l \frac{d[C]}{dt}\)

Q26

How is the instantaneous rate of a chemical reaction at a particular time 't' determined from a experimental concentration vs. time curve?

A.By calculating the total change in concentration over the total time. B.By finding the area under the curve between zero and time t. C.By calculating the slope of the tangent drawn to the curve at time t. D.By taking the reciprocal of the reactant concentration at time t.

Q27

Which of the following characteristics correctly describes the rate constant 'k' of a reaction?

A.It depends on the initial concentration of the reactants. B.It is equal to the rate of reaction when the concentration of each reactant is unity. C.Its value remains constant even if the temperature changes. D.It represents the speed at a specific instant during the reaction.

Q28

Which property distinguishes molecularity from the order of a reaction?

A.Molecularity can be zero or fractional. B.Order is always a whole number and cannot be zero. C.Molecularity is always a whole number and cannot be zero or fractional. D.Order is assigned for each individual elementary step.

Q29

What is the order of the reaction for the decomposition of dinitrogen pentoxide (\(N_2O_5\))?

A.Zero order B.First order C.Second order D.Third order

Q30

Which condition allows a higher-order reaction to be studied as a pseudo-first order reaction?

A.Carrying out the reaction at a very high pressure. B.Taking one of the reactants in large excess. C.Using a heterogeneous catalyst. D.Decreasing the temperature to near absolute zero.

Q31

For a zero-order reaction, a plot of reactant concentration \([A]\) versus time yields a straight line. What does the slope of this line represent?

A.The rate constant \(k\) B.The negative rate constant \(-k\) C.The initial concentration \([A]_0\) D.The natural logarithm of the rate constant \(\\ln k\)

Q32

How does the half-life (\(t_{1/2}\)) of a first-order reaction change if the initial concentration of the reactant is doubled?

A.The half-life also doubles. B.The half-life is reduced by half. C.The half-life remains unchanged. D.The half-life increases by a factor of four.

Q33

Which of the following is true for the half-life of a zero-order reaction?

A.It is independent of the initial concentration. B.It is inversely proportional to the initial concentration. C.It is directly proportional to the initial concentration. D.It is inversely proportional to the square of the initial concentration.

Q34

According to collision theory, even if molecules collide with sufficient energy, they may not react. What additional factor is necessary for an effective collision?

A.High pressure B.Presence of an inert gas C.Proper orientation of colliding molecules D.Small molecular size

Q35

In the Arrhenius equation \(k = A e^{-E_a/RT}\), what does the term 'A' represent?

A.Activation energy B.Frequency factor C.Gas constant D.Reaction rate

Q36

When plotting \(\\ln k\) versus \(1/T\) based on the Arrhenius equation, a straight line is obtained. What is the slope of this line?

A.\(\\ln A\) B.\(-E_a / R\) C.\(E_a / 2.303 R\) D.\(R / E_a\)

Q37

How does a catalyst affect the rate of a chemical reaction?

A.It increases the rate by increasing the enthalpy of the reaction. B.It decreases the rate by increasing the activation energy. C.It increases the rate by providing an alternative path with lower activation energy. D.It has no effect on the reaction rate.

Q38

In the reaction between marble chips (\(CaCO_3\)) and hydrochloric acid, why does powdered marble react faster than larger chips of the same mass?

A.The powder has a higher temperature. B.The powder has a larger surface area available for collisions. C.The powder acts as a catalyst for the reaction. D.The powder decreases the activation energy of the reaction.

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About this Chemical Kinetics test

This free online practice test covers Chemical Kinetics from the 12th Standard Chemistry (Samacheer Kalvi) syllabus. Choose the number of questions and an optional time limit, then answer and submit — everything is checked in your browser, with the correct answers and a worked explanation shown at the end. For the full solutions to every question in this set, see the solved MCQs page.

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