Question

Heat of reaction for the change $Zn+C{u}^{2+}\left(0.1M\right)\to Z{n}^{2+}\left(1M\right)+Cu$ at ${27}^{o}C$ is:

• A. $-2.17\times {10}^{5}J$
• B. $-2.29\times {10}^{5}J$
• C. $-2.24\times {10}^{5}J$
• D. $-1.84\times {10}^{5}J$

Answer 1

The correct option is A $-2.17\times {10}^{5}J$

The relationship betwen standard emf and standard cell potential is
$E^0=-\frac{\Delta H^0}{nF}+T{\left(\frac{dE}{dT}\right)}_P$
Substitute values in the above reaction.
$1.085=-\frac{\Delta H^0}{2\times 96500}+300\times (1.4\times {10}^{-4})\Delta H^0=-2.17\times {10}^5$