(a)i. State two characteristics of a homologous series.
(ii) Explain briefly why there are differences in the reaction of ethane and ethene.
(b) When crystals of sodium chloride were warmed with concentrated tetraoxosulphate( VI) acid, a gas was evolved.
(i) Name the gas.
(ii) State two physical properties of the gas.
(iii) Write a balanced chemical equation for the reaction.
(c)i. What are hydrocarbons?
(ii) State two natural sources of hydrocarbons.
(iii) A hydrocarbon contains 83% of carbon by mass. Calculate its empirical formula. [H=1.0, C=12.0]
(d) Draw and label a diagram of a set-up that could be used to electroplate a copper ornament with silver
Explanation
(a)i. Characteristics of homologouS series
- All members can be represented by a general formula.
- Each member of the series differs from the next by a constant/fixed number of atoms
- CH\(_{2}\)/ 14 amu
- All members of the series show a gradual change in physical properties such as density.
- AII members have similar chemical properties/same functional groups.
- All members of the group are prepared using a similar chemical method
(ii) Differences in the Reaction of Ethane and Ethene
- Ethane is a saturated hydrocarbon containing a single bond and therefore undergoes mainly substitution reaction while ethene is an unsaturated hydrocarbon containing a double bond and hence undergoes an addition reaction
(b)i. The gas is hydrogen chloride.
(ii) Physical properties of the gas:
- Colourless
- Has choking smell
- Denser than air
- Gas is soluble in water.
- Gas fumes in moist air.
(iii) Write a balanced equation reaction:
2HaCl\(_{(s)}\) + H,SO\(_{4(aq)}\), \(\implies\) Na2SO\(_{4(aq)}\) + 2HC\(_{(g)}\) OR HaCI\(_{(s)}\) + H\(_{2}\)SO\(_{4(aq)}\) \(\implies\) NaHSO\(_{4(aq)}\) + HCl\(_{(g)}\)
(c)i. Hydrocarbons are compounds containing only hydrogen and carbon
(ii) Two Natural Sources of Hydrocarbons:
- Coal
- Petroleum/crude oil Natural gas.
(iii) A hydrocarbon contains 83.0 % of carbon by mass. calculate its emprical formular (H =1.0; C = 12.0).
Solution: C = 83.0 %.
\(\therefore\) % H\(_{2}\) = 100 - 83 17%
(d) Draw and label a diagram of a set-up that could be used to electroplate a copper ornament with silver.
