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. `594 nm`
B. `640 nm`
C. `700 nm`
D. `494 nm`

Answer

4

Explanation

`Cl-Cl(g) rarr 2Cl(g), deltaH=242 KJ mol=(242xx10^(3))/(6.02xx10^(23)) J molecule^(-1)`
`E=(hc)/lambda rArr (242xx10^(-23)xx10^(3))/(6.02)=(6.6xx10^(-34)xx3xx10^(8))/lambda`
`lambda=(6.6xx10^(-34)xx3xx10^(8))/(242xx10^(-23)xx10^(3))=(6.6xx3xx6.02)/(242) xx10^(-6)=0.494xx10^(-6)=494xx10^(-9)m=494 nm`