Question

The energy required to break one mole of $Cl-Cl$ bond in ${Cl}_2$ in $242kJ{mol}^{-1}$. The longest wavelength of light capable of breaking a single $Cl-Cl$ bond is:

[$c=3\times {10}^4{ms}^{-1}$ and $N_A=6.02\times {10}^{23}{mol}^{-1}$]

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

Answer 1

Answer: (D)

494 nm

Energy if $Cl-Cl$ bond$=-242kJ/㏖=4.02\times {10}^{-19}J/㏖$

Now,$\frac{hc}{\lambda }=E\Rightarrow \lambda =\frac{hc}{E}=\frac{hc}{4.02\times {10}^{-19}}$

$=494㎚$

Hence, the correct option is $\text{D}$