Answer
(i) $2.25\times 10^{20}$ $J$
(ii) $9\times 10^{20}$ $J$
Work Step by Step
The total work needed to stretch a bond by a displacement $x$ is given by
$W=\frac{1}{2}kx^2$
where $k$ is force constant.
The force constant of a $CāH$ bond is given: $k= 450$ $Nm^{ā1}$
(i) Now the work needed to stretch the bond by $x=10$ $pm$ is
$W=\frac{1}{2}\times 450\times (10\times 10^{-12})^2$ $J$ $=2.25\times 10^{20}$ $J$
(ii) Now the work needed to stretch the bond by $x=20$ $pm$ is
$W=\frac{1}{2}\times 450\times (20\times 10^{-12})^2$ $J$ $=9\times 10^{20}$ $J$
