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Chemical Kinetics

JEE Mains Chemistry. Try each one first, then open its answer.

Top 10 JEE Mains PYQs to practise first

The questions and kinds of question asked most often come first. Each one says how often and in which papers.

  1. Question 1

    This type asked 7 times: 26 Jul 2022, 25 Jan 2023, 30 Jan 2023, 31 Jan 2024, 29 Jan 2025, 5 Apr 2026 S1, 6 Apr 2026 S1. This one: 6 Apr 2026 S1 See all 7 of this type

    49
    Sucrose hydrolyses in acidic medium into glucose and fructose by first order rate law with t1/2=3t_{1/2} = 3 hour. The percentage of sucrose remaining after 6 hours is ____\_\_\_\_ . (Nearest integer) (Given : log⁡2=0.3010\log2 = 0.3010 and log⁡3=0.4771\log3 = 0.4771 )

  2. Question 2

    This type asked 7 times: 2021 Paper 22, 14 Jun 2022, 28 Jun 2022, 13 Apr 2023, 27 Jan 2024, 6 Apr 2024, 28 Jan 2026 S1. This one: 28 Jan 2026 S1 See all 7 of this type

    32
    An organic compound undergoes first order decomposition. The time taken for decomposition to (18)th \left( \frac{1}{8} \right)^{\text{th~}} and (110)th \left( \frac{1}{10} \right)^{\text{th~}} of its initial concentration are t1/8t_{1/8} and t1/10t_{1/10} respectively. What is the value of t1/8t1/10×10\frac{t_{1/8}}{t_{1/10}}\times 10 ?
    (log⁡2=0.3)(\log2 = 0.3)

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  3. Question 3

    This type asked 6 times: 13 Apr 2023, 1 Feb 2024, 9 Apr 2024, 23 Jan 2025, 7 Apr 2025, 21 Jan 2026 S2. This one: 21 Jan 2026 S2 See all 6 of this type

    33
    Decomposition of A is a first order reaction at T(K)T(K) and is given by A(g)→B(g)+C(g)A(g) \rightarrow B(g) + C(g). In a closed 1 L vessel, 1 bar A(g)A(g) is allowed to decompose at T(K)T(K). After 100 minutes, the total pressure was 1.5 bar. What is the rate constant (in min⁡−1\min^{- 1}) of the reaction ? (log⁡2=0.3\log2 = 0.3)

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  4. Question 4

    This type asked 5 times: 2021 Paper 23, 27 Jun 2022, 29 Jun 2022, 22 Jan 2026 S2, 6 Apr 2026 S2. This one: 6 Apr 2026 S2 See all 5 of this type

    50
    Decomposition of a hydrocarbon follows the equation k=(5.5×1011 s−1)e−28000 K Tk = \left( 5.5 \times 10^{11}{\text{ }s}^{- 1} \right)e^{\frac{- 28000\text{ }K}{\text{ }T}}. The activation energy of reaction is ____\_\_\_\_ kJmol−1kJ{mol}^{- 1}. (Nearest Integer) Given : R=8.3JK−1 mol−1R = 8.3{JK}^{- 1}{\text{ }mol}^{- 1}

  5. Question 5

    This type asked 5 times: 2021 Paper 21, 27 Jun 2022, 29 Jun 2022, 31 Jan 2023, 2 Apr 2026 S1. This one: 2 Apr 2026 S1 See all 5 of this type

    49
    For reaction A→PA \rightarrow P, rate constant k=1.5×103 s−1k = 1.5 \times 10^{3}{\text{ }s}^{- 1} at 27∘C27^{\circ}C. If activation energy for the above reaction is 60 kJ mol−160\text{ }kJ{\text{ }mol}^{- 1}, then the temperature (in  ∘C\ ^{\circ}C ) at which rate constant, k=4.5×103 s−1k = 4.5 \times 10^{3}{\text{ }s}^{- 1} is ____\_\_\_\_ . (Nearest integer) Given : log⁡2=0.30,log⁡3=0.48,R=8.3 J K−1 mol−1\log2 = 0.30,\log3 = 0.48,R = 8.3\text{ }J{\text{ }K}^{- 1}{\text{ }mol}^{- 1}, ln⁡10=2.3\ln10 = 2.3

  6. Question 6

    This type asked 5 times: 28 Jun 2022, 29 Jul 2022, 29 Jan 2024, 1 Feb 2024, 24 Jan 2026 S2. This one: 24 Jan 2026 S2 See all 5 of this type

    47
    The half-life of  65Zn\ ^{65}Zn is 245 days. After x days, 75%75\% of original activity remained. The value of x in days is ____\_\_\_\_ . (Nearest integer) (Given : log⁡3=0.4771\log3 = 0.4771 and log⁡2=0.3010\log2 = 0.3010 )

  7. Question 7

    This type asked 5 times: 2021 Paper 20, 25 Jun 2022, 11 Apr 2023, 30 Jan 2024, 23 Jan 2026 S2. This one: 23 Jan 2026 S2 See all 5 of this type

    36
    Observe the following reactions at T(K)T(K) (I) A → products. (II) 5Br−(aq)+BrO3−(aq)+6H+(aq)→3Br2(aq)+3H2O(l)5{Br}^{-}(aq) + {BrO}_{3}^{-}(aq) + 6H^{+}(aq) \rightarrow 3{Br}_{2}(aq) + 3H_{2}O(l) Both the reactions are started at 10.00 am . The rates of these reactions at 10.10 am are same. The value of −Δ[Br−]Δt-\frac{\Delta\left\lbrack Br^{-} \right\rbrack}{\Delta t} at 10.10 am is 2×10−4 mol L−1Min−12 \times10^{- 4}\text{ }mol{\text{ }L}^{- 1}Min^{- 1}. The concentration of A at 10.10 am is 10−2 mol L−110^{- 2}\text{ }mol{\text{ }L}^{- 1}. What is the first order rate constant (in min⁡−1\min^{- 1} ) of reaction I?

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  8. Question 8

    This type asked 5 times: 5 Apr 2024, 9 Apr 2024, 28 Jan 2025, 4 Apr 2025, 22 Jan 2026 S1. This one: 22 Jan 2026 S1 See all 5 of this type

    37
    A → products (First order reaction). Three sets of experiment were performed for a reaction under similar experimental conditions. Run 1⇒100 mL1 \Rightarrow 100\text{ }mL of 10 M solution of reactant A Run 2⇒200 mL2 \Rightarrow 200\text{ }mL of 10 M solution of reactant A Run 3⇒100 mL3 \Rightarrow 100\text{ }mL of 10 M solution of reactant A+A + 100 mL of H2OH_{2}O added. The correct variation of rate of reaction is

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  9. Question 9

    This type asked 5 times: 25 Jun 2022, 25 Jul 2022, 26 Jul 2022, 24 Jan 2023, 28 Jan 2025. This one: 28 Jan 2025 See all 5 of this type

    32
    For a given reaction R→P,t1/2R \rightarrow P,t_{1/2} is related to [A]0\lbrack A\rbrack_{0} as given in table :
    [A]0/molL−1\lbrack A\rbrack_{0}/molL^{- 1}t1/2/mint_{1/2}/min
    0.100200
    0.025100
    Given : log2=0.30log2 = 0.30 Which of the following is true? (A) The order of the reaction is 12\frac{1}{2}. (B) If [A]0\lbrack A\rbrack_{0} is 1 M , then t1/2t_{1/2} is 20010 min⁡200\sqrt{10}\text{ }\min (C) The order of the reaction changes to 1 if the concentration of reactant changes from 0.100 M to 0.500 M . (D) t1/2t_{1/2} is 800 min for [A]0=1.6M\lbrack A\rbrack_{0}= 1.6M Choose the correct answer from the options given below :

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  10. Question 10

    This type asked 4 times: 2021 Paper 12, 2021 Paper 17, 30 Jan 2024, 4 Apr 2026 S2. This one: 4 Apr 2026 S2 See all 4 of this type

    49
    For a first order reaction A→BA \rightarrow B
    tt/min[A][A]/M
    00.6500
    xx0.0650
    200.00065
    x=x = ____\_\_\_\_ min. (Nearest integer)