Chemical Kinetics · JEE Main previous year questions

2019 6 questions

1. Q692019 · 10 Apr 2019 · Shift 2

   For the reaction of ${\mathrm{H}}_2$ with ${\mathrm{I}}_2$, the rate constant is $2.5\times 10^{-4}\mathrm{d}{\mathrm{m}}^3\mathrm{mo}{\mathrm{l}}^{-1}{\mathrm{s}}^{-1}$ at $327^{\circ }\mathrm{C}$ and $1.0\mathrm{d}{\mathrm{m}}^3\mathrm{mo}{\mathrm{l}}^{-1}{\mathrm{s}}^{-1}$ at $527^{\circ }\mathrm{C}$. The activation energy for the reaction, in $\mathrm{kJ}\mathrm{mol}{\mathrm{e}}^{-1}$ is : ($\mathrm{R}=8.314\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ )

   1. A.59
   2. B.166
   3. C.72
   4. D.150
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   Answer: B

2. Q712019 · 9 Apr 2019 · Shift 2

   In the following reaction $$\mathrm{Carbonyl}\mathrm{compound}+\mathrm{MeOH}\stackrel{\mathrm{HCl}}{\rightleftharpoons }\mathrm{acetal}$$ Rate of the reaction is the highest for :

   1. A.Propanal as substrate and methanol in stoichiometric amount.
   2. B.Acetone as substrate and methanol in stoichiometric amount
   3. C.Propanal as substrate and methanol in excess
   4. D.Acetone as substrate and methanol in excess
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   Answer: C

3. Q742019 · 12 Jan 2019 · Shift 1

   Decomposition of X exhibits a rate constant of $0.05\mu g/year$. How many years are required for the decomposition of $5\mu \mathrm{g}$ of X into $2.5\mu \mathrm{g}$?

   1. A.50
   2. B.20
   3. C.25
   4. D.40
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   Answer: A

4. Q712019 · 12 Jan 2019 · Shift 2

   For a reaction consider the plot of $\ln k$ versus $1/T$ given in the figure. If the rate constant of this reaction at 400 K is $10^{-5}{\mathrm{s}}^{-1}$, then the rate constant at 500 K is – [Figure: straight line plot of $\ln k$ vs $1/T$, Slope = −4606 K]

   1. A.$10^{-4}{\mathrm{s}}^{-1}$
   2. B.$4\times 10^{-4}{\mathrm{s}}^{-1}$
   3. C.$10^{-6}{\mathrm{s}}^{-1}$
   4. D.$2\times 10^{-4}{\mathrm{s}}^{-1}$
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   Answer: A

5. Q712019 · 11 Jan 2019 · Shift 2

   The reaction $2\mathrm{X}\to \mathrm{B}$ is a zeroth order reaction. If the initial concentration of X is $0.2\text{ M}$, the half-life is $6\text{ h}$. When the initial concentration of X is $0.5\text{ M}$, the time required to reach its final concentration of $0.2\text{ M}$ will be:

   1. A.$18.0\text{ h}$
   2. B.$9.0\text{ h}$
   3. C.$7.2\text{ h}$
   4. D.$12.0\text{ h}$
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   Answer: A

6. Q772019 · 9 Jan 2019 · Shift 1

   The following results were obtained during kinetic studies of the reaction ; $$2\mathrm{A}+\mathrm{B}\to \text{Products}$$ $$\begin{array}{llll}\text{Experiment}& {\text{[A] (in mol L}}^{-1}\text{)}& {\text{[B] (in mol L}}^{-1}\text{)}& {\text{Initial Rate of reaction (in mol L}}^{-1}{\text{ min}}^{-1}\text{)}\\ \text{I}& 0.10& 0.20& 6.93\times 10^{-3}\\ \text{II}& 0.10& 0.25& 6.93\times 10^{-3}\\ \text{III}& 0.20& 0.30& 1.386\times 10^{-2}\end{array}$$ The time (in minutes) required to consume half of A is :

   1. A.5
   2. B.10
   3. C.1
   4. D.100
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   Answer: A