Chemistry MCQs for NEET — Practice Questions with Answers

(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${}^{-1}$

(a) C₁₂H₂₂O₁₁ $\stackrel{\mathrm{Maltase}}{\to }$ 2C₆H₁₂O₆

       Maltose                     Glucose

(d) Fe₄[Fe(CN)₆]₃ sol is Prussian blue sol of + ve charge.

(d) MnO₂ speeds up the reaction.

(c) Enzyme catalysed reactions are highly specific, i.e., one enzyme catalyses one reaction.

(b) If BaSO₄ is not used, the reaction will give alcohol. BaSO₄ retards the activity of Pd.

             RCOCl $\underset{\mathrm{Pd}/{\mathrm{BaSO}}_4}{\overset{{\mathrm{H}}_2}{\to }}$ RCHO

             RCOCl$\underset{\mathrm{Pd}}{\overset{{\mathrm{H}}_2}{\to }}$RCHO$\to$RCH₂OH

Most of the enzymes have proteinous nature. They are highly specific and get denaturated by high temperature or UV rays. At optimum temperature, which is generally in between 25°-35°C, enzyme activity is maximum.

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