Question

The energy required to break one mole of Cl–Cl bonds in $C{l}_2$ is $242kJmo{l}^{-1}$. The longest wavelength of light capable of breaking single Cl-Cl bond is $(c=3\times {10}^{8}mse{c}^{-1}$, $N_A=6.023\times {10}^{23}mo{l}^{-1})$

• A. 700 nm
• B. 494 nm
• C. 594 nm
• D. 640 nm

Answer 1

The correct option is B 494 nm

Bond energy of single bond = $\frac{242}{6.023\times {10}^{23}}=4.017\times {10}^{-22}KJ=4.017\times {10}^{-19}J$
Now $E=\frac{hc}{\lambda }$ or $\lambda =\frac{hc}{E}$
$=\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{4.017\times {10}^{-19}}=494nm$