Name the process used to:
(a) produce ammonia from nitrogen
(b) produce lead from molten lead(II) bromide
(c) separate an insoluble solid from a mixture of an insoluble solid and a solution
(d) produce ethanol from ethene
(e) identify the components of a mixture of soluble coloured substances
(f) separate a mixture of several liquids with different boiling points
(g) determine the volume of an acid required to neutralise a given volume of an alkali.
Most-appropriate topic codes (Cambridge IGCSE Chemistry 0620):
• Topic 6.3 — Reversible reactions and equilibrium (Haber process) (a)
• Topic 4.1 — Electrolysis (b)
• Topic 12.4 — Separation and purification (c, f)
• Topic 11.6 — Alcohols (Manufacture of ethanol) (d)
• Topic 12.3 — Chromatography (e)
• Topic 12.2 — Acid-base titrations (g)
(a) Haber process
Detailed solution: The Haber process is the industrial method for fixing atmospheric nitrogen. It reacts nitrogen (from air) with hydrogen (from methane) under high pressure and temperature with an iron catalyst to produce ammonia.
(b) electrolysis
Detailed solution: Electrolysis uses electrical energy to decompose molten ionic compounds. For molten lead(II) bromide, passing a current causes lead ions (Pb²⁺) to migrate to the cathode and gain electrons, forming liquid lead metal.
(c) filtration
Detailed solution: Filtration separates a solid from a liquid using a porous barrier (filter paper). The insoluble solid remains as the residue, while the solution passes through as the filtrate.
(d) catalytic addition
Detailed solution: Ethanol is manufactured industrially by the catalytic addition of steam to ethene. This requires a phosphoric acid catalyst at high temperature (300°C) and high pressure (60-70 atm).
(e) chromatography
Detailed solution: Paper chromatography separates soluble coloured substances based on their differing solubilities in a solvent. As the solvent moves up the paper, each component travels a different distance, producing a distinct spot.
(f) fractional distillation
Detailed solution: Fractional distillation separates liquids with different boiling points. The mixture is heated, and vapours rise up a fractionating column; components condense at different heights based on their boiling points.
(g) titration
Detailed solution: Titration is a quantitative technique where a solution of known concentration (in a burette) is added to a known volume of another solution until neutralisation occurs, indicated by a colour change of an indicator.
