Chemistry Past Questions and Answers

(a) Give two reasons why carbon(IV) oxide is used for extinguishing fire
(b) Explain briefly the water softening action of cation exchane resins.

A hydrocarbon X which decolorizes bromine water but has no action on ammoniacal silver trioxonitrate (V) solution was found to have a molar mass of 58 g mol\(^{-1}\)
(a) Deduce the molecular formula of X. (H = 1, C = 12)
(b) Write the structures of two isomers of X.

(a) Balance the nuclear equation below and hence identify Y.
\(^{238}_{94}U \to ^{234}_{92}Th + Y\)
(b) In a tabular form, state two of the observations in the cathode ray experiment and the corresponding deductions.

(a) Give one reason why a collision between reactants may not produce new species.
(b) Explain, illustrating with appropriate equation(s), why an aqueous solution of aluminium chloride is acidic.

(a) Give the formula indicating the relationship between entropy, free energy and enthalpy changes of a system.
(b) For each of the following, state whether entropy change is positive, negative or zero.
(i) H\(_2\)O\(_{(g)}\) -> H\(_2\)O\(_{(g)}\)
(ii) Cl\(_{2(g)}\) ---> 2CI\(_{(g)}\)
(iii) HCI\(_{(g)}\) -> HCl\(_{(g)}\)