(a) (i) State Boyle’s law.
(ii) Give the mathematical expression of Boyle’s law.
(iii) Sketch the graphical representation of Boyle’s law.
(b) A given mass of gas occupied 500 cm3 at 30°C and 6.5 x 104 Nm(^{-2}). Calculate the volume of the gas at s.t.p. [ Standard pressure = 1.01 x 105 Nm(^{-2})]
(c) Explain why an inflated balloon expands in warm water.
(d)(i) What is meant by the term vapour density? (ii) Determine the vapour density of SO(_{2}). [ S = 32, O = 16 ]
(e)(i) Which of the following gases, SO(_{2}) and NH(_{3}) can be collected by I. upward delivery; II. downward delivery?
(ii) What would be the nature of the solution formed by dissolving each of the following substances in water separately. I. SO(_{2}) II. NH(_{3})
(iii) State the property exhibited by SO(_{2}) and NH(_{3}) in the following equations:
I. 2H(_{2})S(_{(aq)}) + SO(_{2(g)}) (to) 3S(_{(s)}) + 2H(_{2})O(_{(/)})
II. 3CuO(_{(s)}) + 2NH(_{3(g)}) (to) 3Cu(_{(s)}) + 3H(_{2})O(_{(/)}) + N(_{2(s)}).
(f) State two alloys of tin.
(ii) Give one use of each of the alloys in (f)(i).
Explanation
(i) Boyle’s law states that the volume of a given mass of gas is inversely proportional to its pressure if the temperature remains constant.
(ii) P (propto) 1 or PV = K or V (propto) (frac{1}{P})
(iii)
(frac{P_1V_1}{T_1} = frac{P_2V_2}{T_2})
(V_2 = frac{P_1V_1T_2}{P_2T_1})
(V_2 = frac{6.5 times 10^4 times 500 times 273}{(273 + 30) times 1.01 times 10^5})
(V_2 = 290 cm^3)
(c) An inflated balloon expands in warm water because in air, particles in the balloon acquire more kinetic energy. There is an increase in the pressure inside the balloon. In order to keep the pressure constant the balloon expands.
(d) (i) Vapour density is the number of times a given volume of a gas or vapour is as heavy as an equal volume of hydrogen gas at the same temperature and pressure.
(ii) molar mass of SO(_2) = 32 + 16 x 2 = 64g mol(^{-1}).
Vapour density x 2 = relative molar mass
Vapour density = (frac{64}{32})
= 32
(e) (i) I. upward delivery = NH(_3)
II. downward delivery = SO(_2)
(ii) I. acidic II. basic/alkaline
(iii) SO(_2) – oxidizing agent NH(_3) – reducing agent.
(f) (i) – bronze – typemetal – soft solder
(ii) bronze – for making coins, – metals/other ornaments
typemetal – for printing
soft solder – for plumbing/welding.