The energy required to break one mole of `Cl-Cl` bonds in `Cl_2` is `242 kJ mol^-1`. The longest wavelength of light capable of breaking a since `Cl-Cl` bond is

Options

A. ` 1035 nm`
B. ` 325 nm`
C. ` 742 nm`
D. ` 518 nm`

Answer

D

Explanation

Energy required for dissociation fo one ` Cl_2` molecule ` = ( 242 xx 10^3)/N_A ` joules .
This enrgy is contiained in photon fo waverngth
` lambda`
`( 242 xx 10^3)/( 6.022 xx 10^(23)) = ( hc)/(lambda) = ( 6.6 xx 10^(-34 )xx 3 xx 10^8)/(lambda )`
`rArr lambda = 494 nm`.