In following equations, calculate the moles of substances numbers denoted by letters a - f:

1.           CO_(g)     +    Cl_2(g)    ⇔     COCl_2(g)

At start   1 mole          2 moles         0 moles

At equilm  0.5 moles         a                 b

2.          N_2(g)       +     3H_2(g)   ⇔     2NH_3(g)

At start  1 mole            3 moles         0 moles

At equilm  c                     d              1.2 moles

3.           NH₂COONH_4(s)       ⇔       2NH_3(g)    +    CO_2(g)
At start           e                           0 moles          0 moles
At equilm    2 moles                        2 moles            f

4. An important reaction in the manufacture of sulphuric acid is:

                                2SO_2(g) + O_2(g) ⇔ 2SO_3(g) ΔH = -197 kJ mol^-1

This reaction was intensively investigated by Bodenstein in 1905. In one of his experiments he found that at 1000K, equilibrium occurred when the partial pressures of the gasses in the mixture were as follows:

P_SO2 = 0.456 atmospheres P_O2 = 0.180 atmospheres P_SO3 = 0.364 atmospheres

(a) What does the term partial pressure mean?

(b) Write an expression for the equilibrium constant K_P for this in terms of partial pressures

(c) Use the partial pressures given above to calculate the value of Kp at 1000K, including its units

(d) What would be the effects on the value of Kp, if the following changes were made to the system:

(i) the partial pressure of oxygen is increased by 0.100 atmosphere
(ii) the temperature was lowered to 800K

5. Explain the difference between the following terms, shown in italics, giving suitable examples:

(a) strong and concentrated when applied to acids

6. Aspirin is a weak monobasic acid, Representing aspirin as HAsp and its conjugate base as Asp explain how a solution containing aspirin and its sodium salt can function as a buffer solution. Your answer MUST contain chemical equations.

7. Aspirin is a weak monobasic acid. The acid dissociation constant Ka for aspirin is 3.27 x 10^-4 mol dm^-3 at 25 C. A chemist wishes to make a buffer solution with a pH of 4.00 using aspirin and its sodium salt. The chemist starts with a solution containing 0.05 mol dm^-3 aspirin.

(a) Calculate the pH of the aspirin solution

(b) Calculate [H₃O⁺] for a solution with pH = 4.00

(c) Calculate the concentration of the sodium salt of aspirin required to produce a solution with a pH of 4.00

8. Balance the following redox equations, using the oxidation number method:

(a) SO₃^2-_(g) + C_e⁴⁺(_aq) + H₂O_(I) → SO₄^2- _(aq) + Ce³⁺_(aq) + H⁺ _(aq)

(b) Br_2(aq) + OH^-_(aq) → Br^-_(aq) + BrO₃^-_(aq) + H₂O_(I)

(c) Explain what type of reaction is (b)?

9. Cresolphthalein is a common acid - base indicator which changes colour over with the pH range 8.2 9.8.

Would cresolphthalein be a suitable indicator for the titration between 25.0 cm^-3 of 0.1 mol dm^-3 citric acid and 0.1 mol dm^-3 ammonia? Explain your answer. What other method could be used to identify the end-point of this titration?