(a)(i) Define the term hygroscopic.

(ii) Give two difference: between a physical change and a chemical change.

(iii) Using the kinetic theory of gases, explain briefly the Charles' law.

(b)(i) Arrange the following compounds in order of increasing boiling points: CS\(_2\); CO\(_2\); NaH. Give reasons for your answer.

(ii) Write a balanced chemical equation to illustrate the reaction of chlorine gas with cold dilute sodium hydroxide.

(c) In a certain reaction, 15.0 g of impure magnesium sample reacted with excess hydrochloric acid liberating 8.6 dm\(^2\) of hydrogen gas at s.t.p.

(i) Write a balanced equation for the reaction.

(ii) Calculate the: I. mass of pure magnesium in the sample; I. percentage purity of the magnesium sample; III. number of ions produced in the reaction. [Mg = 24.0; volume at s.t.p. 22.4 dm\(^{-3}\), Avagadro's constant = 6.02 x 10\(^{23}\)mol\(^{-1}\)]