Using the Thermodynamic Data Provided Below, Calculate K_a for HCN(aq) $\circ$

question 41

Multiple Choice

Using the thermodynamic data provided below, calculate K_a for HCN(aq) at 25 ^$\circ$ . $\begin{array}{|l|c|c|}\hline & \Delta \mathrm{H}^\circ_{\mathrm{f}}(\mathrm{~kJ} / \mathrm{mol}) & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol}) \\\hline \mathrm{H}^{+}(a q) & 0 & 0 \\\hline \mathrm{CN}^{-}(a q) & 151.0 & 117.99 \\\hline \mathrm{HCN}(a q) & 105.4 & 128.9 \\\hline\end{array}$

• A) 2.4 * 10^-9
• B) 2.6 * 10^-9
• C) 2.8 * 10^-9
• D) 3.0 * 10^-9
• E) None of the above

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