Question

The electron affinity of chlorine is $3.7\, eV. \,1$ gram of chlorine is completely converted to $Cl^-$ ion in a gaseous state. $(1\, eV = 23.06\, kcal\, mol^{-1})$. Energy released in the process is

• A. $4.8 \,kcal$
• B. $7.2 \,kcal$
• C. $8.2 \,kcal$
• D. $2.4 \,kcal$

Answer 1

Answer: (D)

Number of moles $=\frac{1}{35.5}$
Given, $1 eV = 23.06\, kcal\, mol^{-1}$
$3.7 eV = 3.7 \times 23.06\, kcal\, mol^{-1}$
i.e. 1 mole realease energy
$=3.7\times23.06\,kcal$
$\therefore $ Energy released
$=\frac{1}{35.5}\times3.7\times23.06\,kcal=2.4\,kcal$