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Thermodynamics

# Calculate the standard free energy change for the following reaction  $Zn(s) + Cu^{2+} (aq) \rightarrow Cu(s) + Zn^{2+} (aq)$  Given that $\Delta G_f^{\circ}\: for \: Cu^{2+} (aq)\: and \: Zn^{2+} (aq)$ as 65 kJ/mol and -147.2 kJ/mol respectively.

$\begin {array} {1 1} (A)\;212.2\: kJ & \quad (B)\;-212.2 \: kJ \\ (C)\;82.2\: kJ & \quad (D)\;-82.2\: kJ \end {array}$

$\Delta G^{\circ} = \sum \Delta G_f^{\circ} (products) - \sum \Delta G_f^{\circ} (reactants) = [0 + (-147.2)] – [0 + 65] = -147.2 – 65 = -212.2\: kJ$
Ans : (B)