Instructions for Enthalpy Mini Lab Report

This will be an individual lab report. Each group will perform the experiment and collect the data but the actual writing is to be done on an individual basis.

The lab report will require a results section and answers to the questions listed below. The lab report must be typed in 12 point font and all sections must be in the same font. Clearly indicate the sections of the lab report.

Results: This section should contain an explanation of what was done in mixing the 1.0 M HCl and the 1.0 M NaOH. The data should be recorded in such a way that it can be used to calculate the heat of the reaction for H+ + OH- à H₂O. Be sure to correct for the heat capacity of the calorimeter. Compare the your measured enthalpy for the reaction with that calculated by heats of formation. Offer an explanation if different significantly (> 5% from explected). For the mass of the water use a density of 1.05 g/mL.

Questions: Answer the following questions:

1. In this experiment we used a specific heat for the solution that was equal to that of water. How would you expect a salt solution to alter the specific heat of water and why? Think in terms of how the polarity of water influences the nature of water.

2. If a mixed solution has a density of 1.02 g/mL and is formed by mixing 35 mL of A and 55 mL of B, both initially at 22.4°C, what will be the enthalpy of the reaction if the temperature of the combined solution rises to 29.4°C?

3. What will be the temperature that results from mixing three volumes of water, the first being 25 mL at 34.4°C, the second being 35 mL at 74.8°C, and the third being 85 mL at 14.6°C?

4. Given the following information:

O₃ (g) + NO (g) à NO₂ (g) + O₂ (g) ΔH = -199 kJ

O₂ (g) à 2 O ΔH = +495 kJ

2 O₃ (g) à 3 O₂ (g) ΔH = -427 kJ

use Hess's Law to calculate the ΔH for the reaction:

NO (g) + O (g) à NO₂ (g)

5. Why did we use a density of 1.05 g/mL for the solution in the reaction vessel?