Chemical Kinetics · JEE Main previous year questions

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2025 10 questions

Q542025 · 8 Apr 2025 · Shift 2
In a first order decomposition reaction, the time taken for the decomposition of reactant to one fourth and one eighth of its initial concentration are $t_{1}$ and $t_{2}$ (s), respectively. The ratio $t_{1} / t_{2}$ will be:
1. A. $\frac{4}{3}$
2. B. $\frac{3}{2}$
3. C. $\frac{3}{4}$
4. D. $\frac{2}{3}$
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Answer: D
Q542025 · 4 Apr 2025 · Shift 1
Rate law for a reaction between $A$ and $B$ is given by $r = k [A]^{n} [B]^{m}$ If concentration of $A$ is doubled and concentration of $B$ is halved from their initial value, the ratio of new rate of reaction to the initial rate of reaction $(\frac{r _{2}}{r _{1}})$ is
1. A. $(n - m)$
2. B. $2^{(n - m)}$
3. C. $\frac{1}{2 ^{m + n}}$
4. D. $(m + n)$
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Answer: B
Q522025 · 4 Apr 2025 · Shift 2
1. A. $Ea_{2} > Ea_{1} > Ea_{3}$
2. B. $Ea_{1} > Ea_{3} > Ea_{2}$
3. C. $Ea_{3} > Ea_{2} > Ea_{1}$
4. D. $Ea_{1} > Ea_{2} > Ea_{3}$
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Answer: A
Q592025 · 4 Apr 2025 · Shift 2
Half life of zero order reaction $A \to product$ is $1 hour$ , when initial concentration of reactant is $2.0 mol L^{- 1}$ . The time required to decrease concentration of A from $0.50$ to $0.25 mol L^{- 1}$ is :
1. A. $0.5 hour$
2. B. $15 min$
3. C. $60 min$
4. D. $4 hour$
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Answer: B
Q692025 · 3 Apr 2025 · Shift 1
In a reaction $A + B \to C$ , initial concentrations of $A$ and $B$ are related as $[A]_{0} = 8 [B]_{0}$ . The half lives of $A$ and $B$ are $10 min$ and $40 min$ , respectively. If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?
1. A. $20 min$
2. B. $40 min$
3. C. $80 min$
4. D. $60 min$
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Answer: B
Q612025 · 3 Apr 2025 · Shift 2
Consider the following statements related to temperature dependence of rate constants. Identify the correct statements. A. The Arrhenius equation holds true only for an elementary homogenous reaction. B. The unit of $A$ is same as that of $k$ in Arrhenius equation. C. At a given temperature, a low activation energy means a fast reaction. D. A and $Ea$ as used in Arrhenius equation depend on temperature. E. When $Ea ≫ RT$ , A and $Ea$ become interdependent. Choose the correct answer from the options given below:
1. A.A, C and D Only
2. B.B, D and E Only
3. C.B and C Only
4. D.A and B Only
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Answer: C
Q552025 · 28 Jan 2025 · Shift 1
$[A]_{0} / mol L^{- 1} 0.100 0.025 t_{1/2} / min 200100$ For a given reaction $R \to P$ , $t_{1/2}$ is related to $[A]_{0}$ as given in table. Given: $lo g 2 = 0.30$ Which of the following is true? A. The order of the reaction is $1/2$ . B. If $[A]_{0}$ is $1 M$ , then $t_{1/2}$ is $20010 min$ C. The order of the reaction changes to $1$ if the concentration of reactant changes from $0.100 M$ to $0.500 M$ . D. $t_{1/2}$ is $800 min$ for $[A]_{0} = 1.6 M$ Choose the correct answer from the options given below:
1. A.A and C Only
2. B.A, B and D Only
3. C.A and B Only
4. D.C and D Only
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Answer: B
Q652025 · 24 Jan 2025 · Shift 2
1. A.Both Statement I and Statement II are false
2. B.Statement I is true but Statement II is false
3. C.Statement I is false but Statement II is true
4. D.Both Statement I and Statement II are true
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Answer: B
Q712025 · 24 Jan 2025 · Shift 2· Numerical answer
Consider a complex reaction taking place in three steps with rate constants $k_{1}, k_{2}$ and $k_{3}$ respectively. The overall rate constant $k$ is given by the expression $k = \frac{k _{1} k _{3}}{k _{2}}$ . If the activation energies of the three steps are $60$ , $30$ and $10 kJ mo l^{- 1}$ respectively, then the overall energy of activation in $kJmo l^{- 1}$ is ____ . (Nearest integer)
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Answer: 20
Q612025 · 23 Jan 2025 · Shift 2
1. A.
2. B.
3. C.
4. D.
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Answer: B