For a reaction scheme
Question:

For a reaction scheme $\mathrm{A} \stackrel{k_{1}}{\longrightarrow} \mathrm{B} \stackrel{k_{2}}{\longrightarrow} \mathrm{C}$, if the rate of formation of $B$ is set to be zero then the concentration of $B$ is given by:

1. $\left(k_{1}-k_{2}\right)[\mathrm{A}]$

2. $k_{1} k_{2}[\mathrm{~A}]$

3. $\left(k_{1}+k_{2}\right)[\mathrm{A}]$

4. $\left(\frac{k_{1}}{k_{2}}\right)[\mathrm{A}]$

Correct Option: , 4

Solution:

$\mathrm{A} \stackrel{\mathrm{k}_{1}}{\longrightarrow} \mathrm{B} \stackrel{\mathrm{k}_{2}}{\longrightarrow} \mathrm{C}$

$\frac{\mathrm{d}[\mathrm{B}]}{\mathrm{dt}}=\mathrm{k}_{1}[\mathrm{~A}]-\mathrm{k}_{2}[\mathrm{~B}]=0$

$[\mathrm{B}]=\frac{\mathrm{k}_{1}[\mathrm{~A}]}{\mathrm{k}_{2}}$