Chapter 7, Problem 126FP

In a student experiment to confirm Hess's law, the reaction
$N{H}_3\left(\text{concd aq}\right)+HCI\left(\text{aq}\right)\to N{H}_{4}CI\left(\text{aq}\right)$
was carried out in two different ways. First, 8.00 mL of concentrated was added to 100.0 mL of 1.00 M HCI in a calorimeter. (The $N{H}_2\left(aq\right)$ was slightly in excess.) The reactants were initially at 23.8 °C, and the final temperature after neutralization was 35.8 °C. In the second experiment, air was bubbled through 1000 mL of concentrated $N{H}_2\left(aq\right)$ sweeping out $N{H}_2\left(aq\right)$ (see sketch). The was neutralized in 100.0 mL of 1.00 M HCI. The temperature of the concentrated fell from 19-3 to 13.2 °C. At the same time, the temperature of the 1.00 M HCI rose from 23.8 to 42.9°C as it was neutralized by $N{H}_2\left(aq\right)$ . Assume that all solutions have densities of 1.00 g/mL and specific heat capacities of 4.18 J $g^{-1}°C^{-1}.$
a. Write the two equations and values for the processes occurring in the second experiment, Show that the sum of these two equations is the same as the equation for the reaction in the first experiment.
b. Show that, within the limits of experimental error, $\Delta rH$ for the overall reaction is the same in the two experiments, thereby confirming Hess's law.