Chemical Kinetics MCQs for NEET — Chemistry Questions with Answers

(A). Molecularity of a reaction cannot be determined experimentally because molecularity is assigned to the reactions on the basis of mechanism.

(B). For a first order reaction,

$[A{]}_f [A{]}_0 exp(- kt)$

$$\begin{gathered} [A{]}_0- [A{]}_f= [A{]}_0- [A{]}_0 exp( -kt) [A{]}_0 (1- exp( -kt) \\ or \frac{[A{]}_0- [A{]}_f}{[A{]}_0} (1- exp( -kt) \end{gathered}$$

So, degree of dissocation = (1 – exp (–kt)

For a first order reaction,

$k=A exp\left(-E_a/RT\right)=A exp\left(\frac{J mo{l}^{-1}}{J mo{l}^{-1}{K}^{-1}K}\right)$

Thus, the units of A are the same as that for k. For a first order reaction, the units of k are those of time${}^{-1}$. So the units of A are also those of time${}^{-1}$

(d) MnO₂ speeds up the reaction.

$$\begin{gathered} \left(\mathrm{A}\right). {\mathrm{K}}_1\left(\mathrm{no} \mathrm{catalyst}\right)={\mathrm{Ae}}^{\mathbf{-}{\mathbf{E}}_{\mathbf{a}}\mathbf{/}\mathbf{RT}} \\ {\mathrm{K}}_2\left(\mathrm{catalyst}\right)={\mathrm{Ae}}^{\mathbf{-}{\mathbf{E}}_{\mathbf{a}}\mathbf{-}\mathbf{0}\mathbf{.}\mathbf{8}\mathbf{/}\mathbf{RT}} \\ \frac{{\mathrm{K}}_2}{{\mathrm{K}}_1}={\mathrm{e}}^{\mathbf{0}\mathbf{.}\mathbf{8}\mathbf{/}\mathbf{RT}}={\mathrm{e}}^{\mathbf{0}\mathbf{.}\mathbf{8}\mathbf{/}\mathbf{0}\mathbf{.}\mathbf{002}\mathbf{\times }\mathbf{400}}=2.72 \end{gathered}$$

(A). Physical and chemical adsoptions respond differently to a rise in temperature because

       chemical adsorption requires some activation energy. So, at low temperatures, it is very small

       but increases with a rise in temperature. At higher temperatures, it starts decreasing because

       the adsorbate molecules gain more kinetic energy and are able to leave the surface of the

       adsorbent. While in physical adsorption decreases with a rise in temperature.

(A). Catalyst in general, in the form of finely divided powder because finer is the particle of a solid,

       greater is its surface area. Larger surface leads to the greater adsorption of the reacting

       molecules on the surface. As a result, the reaction rate increases.

Rate of reaction is always depends on slow reaction.

H₂(g)+ 2ICl(g) $\to$ 2HCl(g)+ I₂(g) is first order reaction respect to H₂ and I₂ can be measured with the help of both mechanism A and B.

Refer NCERT, Heading 9.12.1, page-154