1. Referring to the phase diagram for water shown below, identify all of the phases present at points A through G. Name points E and H. What are the temperatures (in degrees C) at points F and G?

2. Why is a solution of NH₄Cl_(aq) acidic?

3. Why is freshwater naturally acidic?

4. Why does Xe have a higher boiling temperature than Ar? Answer in terms of intermolecular forces.

5. Why is HClO a stronger acid than HBrO?

6. Would the solubility of CaF_2(s) increase or decrease as the pH is raised? Why? (HF_(aq) is a weak acid.)

Part B. Answer one of the following two questions. (20 marks). If you answer both, the best one will be used to calculate your mark for part B.

1. A solution is made by dissolving 3.00 mole of CaCl_2(s) in enough water to make 2.00 L of solution. The density of the solution is 1.25 g/mL.

(a) Calculate the molality of the solution (not the molarity!)
(b) Calculate the freezing point (^oC) of the solution. (For water, K_f = 1.86^oC kg mol^-1)
(c) Calculate the boiling point (^oC) of the solution. (For water, K_b = 0.51^oC kg mol^-1.)
(d) Calculate the osmotic pressure (atm) of the solution at 25^oC. (R = 0.082 L atm K^-1mol^-1)
(e) Calculate the vapor pressure (mm Hg) of the solution at 25^oC. (The vapor pressure of pure water at 25^oC is 23.8 mm Hg.)

2. The normal boiling point of isooctane (a component of gasoline) is 99.2^oC and its enthalpy of vaporization is 35.76 kJ/mol. Calculate the vapor pressure of isooctane at 25^oC. R = 8.314 J K^-1 mol^-1.

3. A buffered solution contains 0.25 M NH_3(aq) (K_b = 1.8 x 10^-5) and 0.40 M NH₄Cl_(aq).

(a) Use the Henderson-Hasselbalch equation to calculate the pH of this solution.
(b) 0.05 mol of HCl are added to 1 L of the buffer solution. Calculate the resultant pH.

4. Calculate the pH and concentrations of all species present (i.e. H₂SO₃, HSO₃^-, SO₃^-2 and H₃O⁺) in a 1 M aqueous solution of sulfurous acid, H₂SO₃. For this acid, K_a1 = 0.015 and K_a2 = 6.3 x 10^-8.