Chemical Kinetics · JEE Main previous year questions

For a given chemical reaction ${\gamma }_1\mathrm{A}+{\gamma }_2\mathrm{B}\to {\gamma }_3\mathrm{C}+{\gamma }_4\mathrm{D}$ Concentration of $\mathrm{C}$ changes from $10{\text{ mmol dm}}^{-3}$ to $20{\text{ mmol dm}}^{-3}$ in $10\text{ seconds}$. Rate of appearance of $\mathrm{D}$ is $1.5$ times the rate of disappearance of $\mathrm{B}$ which is twice the rate of disappearance $\mathrm{A}$. The rate of appearance of $\mathrm{D}$ has been experimentally determined to be $9{\text{ mmol dm}}^{-3}{\text{ s}}^{-1}$. Therefore, the rate of reaction is $\underline{}{\text{ mmol dm}}^{-3}{\text{ s}}^{-1}$. (Nearest Integer)

At 345 K, the half life for the decomposition of a sample of a gaseous compound initially at 55.5 kPa was 340 s. When the pressure was 27.8 kPa, the half life was found to be 170 s. The order of the reaction is ____________. [integer answer]

For a first order reaction, the time required for completion of 90% reaction is 'x' times the half life of the reaction. The value of 'x' is (Given : ln 10 = 2.303 and log 2 = 0.3010)

1. A.1.12
2. B.2.43
3. C.3.32
4. D.33.31

1. A.
2. B.
3. C.
4. D.

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Heavy water is used for the study of reaction mechanism. Reason (R) : The rate of reaction for the cleavage of O - H bond is slower than that of O - D bond. Choose the most appropriate answer from the options given below :

1. A.Both (A) and (R) are true but (R) is not the true explanation of (A).
2. B.Both (A) and (R) are true and (R) is the true explanation of (A).
3. C.(A) is false but (R) is true.
4. D.(A) is true but (R) is false.

Select the correct statements (A) Crystalline solids have long range order. (B) Crystalline solids are isotropic (C) Amorphous solid are sometimes called pseudo solids. (D) Amorphous solids soften over a range of temperatures. (E) Amorphous solids have a definite heat of fusion. Choose the most appropriate answer from the options given below.

1. A.(A), (B), (E) only
2. B.(B), (D) only
3. C.(C), (D) only
4. D.(A), (C), (D) only

For the first order reaction $\mathrm{A}\to 2B$, 1 mole of reactant A gives 0.2 moles of B after 100 minutes. The half life of the reaction is __________ min. $[Use:\ln 2=0.69,\ln 10=2.3]$ Properties of logarithms : $\ln x^y=y\ln x$; $\ln \left(\frac{x}{y}\right)=\ln x-\ln y$ (Round off to the nearest integer)

1. A.(b) Zero order (c) and (e) First order
2. B.(a) and (b) Zero order (e) First order
3. C.(b) and (d) Zero order (e) First order
4. D.(a) and (b) Zero order (c) and (e) First order

For a chemical reaction $A\to B$, it was found that concentration of B is increased by 0.2 mol ${\mathrm{L}}^{-}$ in 30 min. The average rate of the reaction is ____ $\times 10^{-1}\mathrm{mol}{\mathrm{L}}^{-1}{\mathrm{h}}^{-1}$. (in nearest integer)

Isotope(s) of hydrogen which emits low energy ${\beta }^{-}$ particles with $t_{1/2}$ value > 12 years is/are

1. A.Protium
2. B.Tritium
3. C.Deuterium
4. D.Deuterium and Tritium

$${\mathrm{N}}_2{\mathrm{O}}_{5(\mathrm{g})}\to 2N{\mathrm{O}}_{2(\mathrm{g})}+\frac{1}{2}{\mathrm{O}}_{2(\mathrm{g})}$$ In the above first order reaction the initial concentration of ${\mathrm{N}}_2{\mathrm{O}}_5$ is $2.40\times 10^{-2}\mathrm{mol}{\mathrm{L}}^{-1}$ at 318 K. The concentration of ${\mathrm{N}}_2{\mathrm{O}}_5$ after 1 hour was $1.60\times 10^{-2}\mathrm{mol}{\mathrm{L}}^{-1}$. The rate constant of the reaction at 318 K is ____ $\times 10^{-3}\mathrm{mi}{\mathrm{n}}^{-1}$. (Nearest integer) [Given : log 3 = 0.477, log 5 = 0.699]

The inactivation rate of a viral preparation is proportional to the amount of virus. In the first minute after preparation, $10\%$ of the virus is inactivated. The rate constant for viral inactivation is ________ $\times 10^{-3}{\text{ min}}^{-1}$. (Nearest integer) [Use : $\ln 10=2.303$; ${\log }_{10}3=0.477$; property of logarithm : $\log x^y=y\log x$]

$2\mathrm{NO}(\mathrm{g})+\mathrm{C}{\mathrm{l}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{NOCl}(\mathrm{s})$ This reaction was studied at $-10^{\circ }$ and the following data was obtained $$\begin{array}{llll}\text{Run}& [NO{]}_0& [C{l}_2{]}_0& r_0\\ 1& 0.10& 0.10& 0.18\\ 2& 0.10& 0.20& 0.35\\ 3& 0.20& 0.20& 1.40\end{array}$$ $[NO{]}_0$ and $[C{l}_2{]}_0$ are the initial concentrations and ${\mathrm{r}}_0$ is the initial reaction rate. The overall order of the reaction is ____. (Round off to the Nearest Integer).

A reaction has a half life of 1 min. The time required for 99.9% completion of the reaction is _________ min. (Round off to the Nearest Integer). [Use : ln 2 = 0.69; ln 10 = 2.3]

The decomposition of formic acid on gold surface follows first order kinetics. If the rate constant at 300 K is $1.0\times 10^{-3}{\text{ s}}^{-1}$ and the activation energy ${\mathrm{E}}_{\mathrm{a}}=11.488{\text{ kJ mol}}^{-1}$, the rate constant at 200 K is _______ $\times 10^{-5}{\text{ s}}^{-1}$. (Round off to the Nearest Integer). (Given : $\mathrm{R}=8.314{\text{ J mol}}^{-1}{\text{ K}}^{-1}$)

An exothermic reaction $\mathrm{X}\to \mathrm{Y}$ has an activation energy $30\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$. If energy change $\Delta \mathrm{E}$ during the reaction is $-20\mathrm{kJ}$, then the activation energy for the reverse reaction in kJ is _________. (Integer answer)

If the activation energy of a reaction is $80.9\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$, the fraction of molecules at 700 K, having enough energy to react to form products is $e^{-x}$. The value of x is _________. (Rounded off to the nearest integer) [Use $\mathrm{R}=8.31\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$]

The rate constant of a reaction increases by five times on increase in temperature from $27^{\circ }\mathrm{C}$ to $52^{\circ }\mathrm{C}$. The value of activation energy in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ is ____. (Rounded off to the nearest integer) $[\mathrm{R}=8.314\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}]$

1. A.$d>b>a>c$
2. B.$d>a>b>c$
3. C.$a>b>c>d$
4. D.$c>a>b>d$

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; $R=8.314\mathrm{J}\mathrm{mo}{\mathrm{l}}^{-1}{\mathrm{K}}^{-1}$ $\ln 3.555=1.268$

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

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, $\mathrm{R}=8.3{\text{ J mol}}^{-1}{\text{ K}}^{-1}$, $\ln \left(\frac{3}{2}\right)=0.4$, $e^{-3}=4.0$)

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.$+6(2.303)\mathrm{RT}$

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.${\mathrm{E}}_{\mathrm{b}}>{\mathrm{E}}_{\mathrm{d}}>{\mathrm{E}}_{\mathrm{c}}>{\mathrm{E}}_{\mathrm{a}}$

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?