Question

If $S^o$ for $H_2,{Cl}_2$ and $HCl$ are $0.13,0.22$ and $0.19{kJK}^{-1}$ ${mol}^{-1}$ respectively. The total change in standard entropy for the reaction
$H_2+{Cl}_2\to 2HCl$ is:

• A. $30{JK}^{-1}$ ${mol}^{-1}$
• B. $40{JK}^{-1}$ ${mol}^{-1}$
• C. $60{JK}^{-1}$ ${mol}^{-1}$
• D. $20{JK}^{-1}$ ${mol}^{-1}$

Answer 1

Answer: (A)

$30{JK}^{-1}$ ${mol}^{-1}$

The total change in standard entropy $=$Entropy of products $-$ entropy of reactants

$=2\left(0.19\right)-(0.13+0.22)$ [here 2 is the stoichiometric coefficient of HCl]$=0.38-0.35=0.03$ KJ/Kmol

$=30$J/Kmol

Hence, the correct option is $\text{A}$