Question

Consider two first order reactions $(1)$ and $(2)$. The graph of $\log [ A ]_{t}$ vs $t$ for the two reactions is shown in figure. Choose the correct relation between half life of the first reaction, $\left( t _{1 / 2}\right)_{1}$ and that of the second reaction, $\left( t _{1 / 2}\right)_{2}$.

• A. $\left( t _{1 / 2}\right)_{1} < \left( t _{1/2}\right)_{2}$
• B. $\left( t _{1 / 2}\right)_{1} > \left( t _{1 / 2}\right)_{2}$
• C. $\left( t _{1 / 2}\right)_{1}=\left( t _{1 / 2}\right)_{2}$
• D. None of these

Answer 1

Answer: (A)

For (i) reaction slope is less than the slope of reaction (ii) hence $k _{1}> k _{2}$ and $\left( t _{1 / 2}\right)_{1}<\left( t _{1 / 2}\right)_{2}$.