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ISC Class 12 Chemical Kinetics — practice questions

Explore 66 free Chemical Kinetics questions in ISC Class 12 Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Chemical Kinetics questions and exercises with answers

Showing questions 1–30 of 66.

For the reaction R -> P, the concentration of R changes from 0.03 M to 0.02 M in 25 minutes. What is the average rate of reaction in M min^-1?Read the answer and worked solution →In the reaction 2A -> Products, the concentration of A decreases from 0.5 mol L^-1 to 0.4 mol L^-1 in 10 minutes. What is the rate of reaction in mol L^-1 min^-1?Read the answer and worked solution →For the reaction 2N2O5(g) -> 4NO2(g) + O2(g), if the rate of reaction is r, what is the rate of formation of NO2?Read the answer and worked solution →A reaction has the rate expression Rate = k[A]^1/2 [B]^3/2. What is the overall order of the reaction?Read the answer and worked solution →A reaction has the rate expression Rate = k[A]^3/2 [B]^-1. What is the overall order of the reaction?Read the answer and worked solution →For the reaction A + B -> Product, the rate law is r = k[A]^1/2 [B]^2. What is the order of the reaction?Read the answer and worked solution →A rate constant is found to have units L mol^-1 s^-1. What is the order of the reaction?Read the answer and worked solution →What are the SI units of the rate constant for a first order reaction?Read the answer and worked solution →What are the SI units of the rate constant for a zero order reaction?Read the answer and worked solution →Which of the following statements about order and molecularity is correct?Read the answer and worked solution →The decomposition of H2O2 catalysed by I^- has rate = k[H2O2][I^-] and proceeds via a slow first step. What is the molecularity of the rate determining step?Read the answer and worked solution →A reaction is second order with respect to a reactant. If the concentration of that reactant is reduced to half, how does the rate change?Read the answer and worked solution →Which expression correctly gives the integrated rate law for a zero order reaction R -> P?Read the answer and worked solution →For a zero order reaction, a plot of [R] against time t gives a straight line. What does the slope of this line equal?Read the answer and worked solution →A first order reaction has a rate constant k = 5.5 x 10^-14 s^-1. What is its half-life?Read the answer and worked solution →For a zero order reaction with initial concentration [R]0 = 0.50 mol L^-1 and rate constant k = 1.0 x 10^-2 mol L^-1 s^-1, what is the half-life?Read the answer and worked solution →For a first order reaction, show that the time required for 99.9% completion is how many times the half-life t1/2?Read the answer and worked solution →A first order reaction takes 40 min for 30% decomposition. What is its half-life? (log(10/7) = 0.155)Read the answer and worked solution →Sucrose decomposes by first order kinetics with t1/2 = 3.00 hours. What fraction of the sucrose sample remains after 6 hours?Read the answer and worked solution →In the Arrhenius plot of ln k versus 1/T, what does the slope of the straight line equal?Read the answer and worked solution →In collision theory, what is meant by the collision frequency (Z)?Read the answer and worked solution →In a pseudo first order reaction, [A]/mol L^-1 reads 0.31 at t = 30 s and 0.17 at t = 60 s. What is the average rate of reaction over this interval in mol L^-1 s^-1?Read the answer and worked solution →It is observed that for many reactions the rate constant nearly doubles for a rise in temperature of how much?Read the answer and worked solution →True or False: Chemical Kinetics (ISC 12)Read the answer and worked solution →Complete the Equation: Kinetics (ISC 12)Read the answer and worked solution →Next Step: Reaction Order (ISC 12)Read the answer and worked solution →Rebuild a sample from its halvesRead the answer and worked solution →Flip and pair: term with meaningRead the answer and worked solution →For a FIRST-ORDER reaction with rate constant $k$, the half-life is given byRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →

Worked practice questions

For the reaction R -> P, the concentration of R changes from 0.03 M to 0.02 M in 25 minutes. What is the average rate of reaction in M min^-1?

  1. 8.0 x 10^-4
  2. 4.0 x 10^-4
  3. 2.0 x 10^-4
  4. 6.0 x 10^-4
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Correct answer: B. 4.0 x 10^-4

1. Average rate $= -\dfrac{\Delta[R]}{\Delta t}$. 2. $\Delta[R] = 0.02 - 0.03 = -0.01\ \text{M}$ over $\Delta t = 25\ \text{min}$. 3. $r_{av} = -\dfrac{-0.01}{25} = 4.0\times10^{-4}\ \text{M min}^{-1}$. 4. Distractor A (8.0 x 10^-4) wrongly omits dividing by time span fully or doubles the result. _Source: syllabus Chemistry Ch 3 "Chemical Kinetics", p.5_

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In the reaction 2A -> Products, the concentration of A decreases from 0.5 mol L^-1 to 0.4 mol L^-1 in 10 minutes. What is the rate of reaction in mol L^-1 min^-1?

  1. 0.020
  2. 0.010
  3. 0.005
  4. 0.001
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Correct answer: C. 0.005

1. For $2A \rightarrow$ Products, rate $= -\dfrac{1}{2}\dfrac{\Delta[A]}{\Delta t}$. 2. $\Delta[A] = 0.4 - 0.5 = -0.1\ \text{mol L}^{-1}$ over $10\ \text{min}$. 3. Rate $= -\dfrac{1}{2}\times\dfrac{-0.1}{10} = \dfrac{0.1}{20} = 0.005\ \text{mol L}^{-1}\text{min}^{-1}$. 4. Distractor B (0.010) forgets to divide by the stoichiometric coefficient 2. _Source: syllabus Chemistry Ch 3 "Chemical Kinetics", p.5_

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For the reaction 2N2O5(g) -> 4NO2(g) + O2(g), if the rate of reaction is r, what is the rate of formation of NO2?

  1. Equal to r
  2. Half of r
  3. Twice r
  4. Four times r
Show answer and solution

Correct answer: D. Four times r

1. Rate $= \dfrac{1}{4}\dfrac{\Delta[NO_2]}{\Delta t} = r$. 2. Rearranging, $\dfrac{\Delta[NO_2]}{\Delta t} = 4r$. 3. So NO2 forms at four times the reaction rate. 4. Distractor B confuses the divisor with multiplier; distractor A ignores the coefficient 4. _Source: syllabus Chemistry Ch 3 "Chemical Kinetics", p.5_

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