Chapter 10, Problem 10.85PAE

10.85 Iodine is not very soluble in water, but it dissolves readily in a solution containing iodide ions by the following reaction:

   ${\text{I}}_{\text{2}}\left(\text{aq}\right)+{\text{I}}^{-}\left(\text{aq}\right)\to {\text{I}}_{\text{3}}{}^{-}\left(\text{aq}\right)$

The following graph shows the results of a study of the temperature dependence of $\Delta \text{G}°$ for this reaction. (The solid line is a best fit to the actual data points.) Notice that the quantity on the y axis is $\Delta \text{G}°/T$ , not just

   $\Delta \text{G}°$. Additional data relevant to this reaction are also given in the table that follows the graph.

(a) Calculate $\Delta \text{G}°$ for this reaction at 298 K. (DO NOT read this value off the graph. Use the data given to calculate a more accurate value.)

(b) Determine $\Delta \text{H}°$ for this reaction. Assume that $\Delta \text{H}°$ is independent of T. (HINT: You will need to use the graph provided to find $\Delta \text{H}°$

. It may help if you realize that the graph is a straight line and then try to write an equation for that line