(a)(i) State Graham’s law of diffusion
(ii) If 100 cm\(^3\) of oxygen diffused in 4 seconds and 50cm\(^3\) of gas Y diffused in 3 seconds, calculate the relative molecular mass of gas Y. (0 = 16)
(b) Consider the following equilibrium reaction: X + 2Y\(_{(g)}\) \(\rightleftharpoons\) XY\(_{2(9)}\) \(\Delta\)H = -52KJ mol\(^{-1}\)
(i) State what happens to the yield of XY\(_2\) when the temperature is increased
(ii) Explain the effect of decrease in pressure on the equilibrium position.
(iii) State the effect of a catalyst on the I. position of equilibrium II. activation energy
(c)(i) State the differences between the solubilities of solids and gases in liquids.
(ii) Name the physical-properties used it choosing separation techniques for the following mixtures:
I. kerosene and petrol II. calcium trioxocarbonate (IV) and potassium chloride. III. ammonium chloride and sodium chloride.
(d)(i) State a method of preparing each of the following salts:
| Acid | Basicity |
| H\(_3\)PO\(_4\) | |
| CH\(_3\)COOH | |
| HNO\(_2\) |
(iii) State the difference between anhydrous and hydrated salts.
Explanation
(a) Graham's Law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of it's vapour density or relative molecular mass.
\(\frac{RO_2}{R_y} = \sqrt{\frac{M_y}{MO_2}}; \frac{\frac{100}{4}}{{\frac{50}{3}}}\)
\(\frac{100}{4}\) x \(\frac{3}{50}\) = \(\sqrt{\frac{M_y}{32}}\)
= \(M_y = \frac{32 \times 9}{4}\) = 72
(b) X\(_{(g)}\) + 2Y\(_{(g)}\) \(\rightleftharpoons\) XY\(_{2(g)}\) \(\Delta\)H = – 52 KJ mol\(^{-1}\)
(i) The yield decreases
(ii) The forward reaction is accompanied by a decrease in the number of gaseous molecules. A decrease in pressure shifts the position of equilibrium to the left favouring the backward reaction.
(iii) i. The position of equilibrium is not affected by the presence of .a catalyst. ii. The presence of a catalyst lowers the activation energy or takes the reaction through another path of lower energy barrier.
(c)(i)
|
Solids in Gases |
Gases in liquid |
|
Solubility increases with increase in temperature |
Solubility decreases with increase in temperature |
|
Solubility is faster with increase in surface area |
Surface area has no effect on solubility |
|
Solubility is not affected by pressure |
Solubility increases with increase in pressure. |
(ii) I. Boiling point II. Solubility III. Sublimation or property of solid.
(d) I. Neutralization II. Double decomposition or precipitation Ill. Displacement or reduction.
|
Acid |
Basicity |
| \(H_3PO_4\) | 3 |
| \(CH_3COOH\) | 1 |
| \(HNO_2\) | 1 |
(iii) Hydrated salts contain water of crystallization while anhydrous salts do not.