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

Answer

A

Explanation

Energy required to break one mole of Cl - Cl bonds `=242 kJ "mol"^(-1)`
Energy required to break one Cl-Cl bond
`=((242xx10^(3) "J mol"^(-1)))/((6.022xx10^(23) "mol"^(-1)))`
=`4.029xx10^(19)J`
We know that `E=(hc)/(lambda)`
`lambda=(hc)/(E)=((6.626xx10^(-34)Js)xx3xx10^(8) ms^(-1))/((4.02xx10^(-19)J))`
`=4.94xx10^(-7)m=494xx10^(-9)m=494 nm`