Chemical Kinetics · JEE Main previous year questions

2020 8 questions

1. Q622020 · 6 Sept 2020 · Shift 1
   
   1. A.$d>b>a>c$
   2. B.$d>a>b>c$
   3. C.$a>b>c>d$
   4. D.$c>a>b>d$
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   Answer: A

2. Q742020 · 6 Sept 2020 · Shift 2· Numerical answer

   The rate of a reaction decreased by 3.555 times when the temperature was changed from $40^{\circ }\mathrm{C}$ to $30^{\circ }\mathrm{C}$. The activation energy (in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$) of the reaction is ______ . Take; $R=8.314\mathrm{J}\mathrm{mo}{\mathrm{l}}^{-1}{\mathrm{K}}^{-1}$ $\ln 3.555=1.268$

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   Answer: 100

3. Q522020 · 9 Jan 2020 · Shift 1

   For the following reactions $A\stackrel{700\mathrm{K}}{\to }\text{Product}$ $A\underset{\text{catalyst}}{\overset{500\mathrm{K}}{\to }}\text{Product}$ it was found that ${\mathrm{E}}_{\mathrm{a}}$ is decreased by 30 kJ/mol in the presence of catalyst. If the rate remains unchanged, the activation energy for catalysed reaction is (Assume pre exponential factor is same):

   1. A.198 kJ/mol
   2. B.135 kJ/mol
   3. C.105 kJ/mol
   4. D.75 kJ/mol
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   Answer: D

4. Q732020 · 9 Jan 2020 · Shift 2· Numerical answer

   A sample of milk splits after 60 min. at 300 K and after 40 min. at 400 K when the population of lactobacillus acidophilus in it doubles. The activation energy (in kJ/ mol) for this process is closest to________. (Given, $\mathrm{R}=8.3{\text{ J mol}}^{-1}{\text{ K}}^{-1}$, $\ln \left(\frac{3}{2}\right)=0.4$, $e^{-3}=4.0$)

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   Answer: 3.98 to 3.99

5. Q612020 · 8 Jan 2020 · Shift 1

   The rate of a certain biochemical reaction at physiological temperature (T) occurs $10^6$ times faster with enzyme than without. The change in the activation energy upon adding enzyme is :

   1. A.$+6\mathrm{RT}$
   2. B.$-6(2.303)\mathrm{RT}$
   3. C.$-6\mathrm{RT}$
   4. D.$+6(2.303)\mathrm{RT}$
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   Answer: B

6. Q522020 · 8 Jan 2020 · Shift 2
   
   1. A.${\mathrm{E}}_{\mathrm{c}}>{\mathrm{E}}_{\mathrm{a}}>{\mathrm{E}}_{\mathrm{d}}>{\mathrm{E}}_{\mathrm{b}}$
   2. B.${\mathrm{E}}_{\mathrm{a}}>{\mathrm{E}}_{\mathrm{c}}>{\mathrm{E}}_{\mathrm{d}}>{\mathrm{E}}_{\mathrm{b}}$
   3. C.${\mathrm{E}}_{\mathrm{b}}>{\mathrm{E}}_{\mathrm{a}}>{\mathrm{E}}_{\mathrm{d}}>{\mathrm{E}}_{\mathrm{c}}$
   4. D.${\mathrm{E}}_{\mathrm{b}}>{\mathrm{E}}_{\mathrm{d}}>{\mathrm{E}}_{\mathrm{c}}>{\mathrm{E}}_{\mathrm{a}}$
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   Answer: A

7. Q732020 · 7 Jan 2020 · Shift 1· Numerical answer

   During the nuclear explosion, one of the products is ${}^{90}\mathrm{Sr}$ with half life of $6.93\text{ years}$. If $1\mu \text{g}$ of ${}^{90}\mathrm{Sr}$ was absorbed in the bones of newly born baby in place of Ca, how much time, in years, is required to reduce it by 90% if it is not lost metabolically?

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   Answer: 23 to 23.03

8. Q572020 · 7 Jan 2020 · Shift 2
   
   1. A.${\mu }_B>{\mu }_A$ and ${\mathrm{K}}_{\mathrm{e}}(\mathrm{A})>{\mathrm{K}}_{\mathrm{e}}(\mathrm{B})$
   2. B.${\mu }_A>{\mu }_B$ and ${\mathrm{K}}_{\mathrm{e}}(\mathrm{B})>{\mathrm{K}}_{\mathrm{e}}(\mathrm{A})$
   3. C.${\mu }_B>{\mu }_A$ and ${\mathrm{K}}_{\mathrm{e}}(\mathrm{B})>{\mathrm{K}}_{\mathrm{e}}(\mathrm{A})$
   4. D.${\mu }_A>{\mu }_B$ and ${\mathrm{K}}_{\mathrm{e}}(\mathrm{A})>{\mathrm{K}}_{\mathrm{e}}(\mathrm{B})$
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   Answer: B