Calculate the wavelength of light required to break the bond between two chlorine atoms in a chlorine molecule. The Cl- Cl bond energy is 243 kJ `mol^(-1) (h=6.6 xx10^(-34)Js,c=3xx10^8m//s, ` Avogadro's number `=6.02xx10^(23)mol^(-1)` )

Options

A. `8.18 xx 10^(-31) m`
B. `6.26 xx 10^(-21) m`
C. `4.91 xx 10^(-7)m`
D. `4.11 xx 10^(-6) m`

Answer

C

Explanation

Energy required to break one `Cl - Cl` bond
`= ("Bond energy per mole")/("Avogado's No.") = (243 xx 10^(3) J)/(6.02 xx 10^(23))`
`= 40.36 xx 10^(-20)J`
`E =hv = h (c)/(lamda)`
`:. lamda = (hc)/(E) = ((6.6 xx 10^(-34) Js) (3 xx 10^(8) ms^(-1)))/(40.36 xx 10^(-20) J)`
`= 4.91 xx 10^(-7) m`