Answers section
Questions 5.3.2(a)
- State and explain, using chemical equations, the observations in each of the four demonstrations (with sulphur, copper, magnesium, and carbon).
- Complete the following general word equations for the oxidation of elements by concentrated sulphuric (VI) acid.
- Metal + Concentrated sulphuric (VI) acid
- Non-metal + Concentrated sulphuric (VI) acid
- Give three reasons why concentrated sulphuric (VI) is exceptionally corrosive, attacking metals and non-metals alike.
- Which other acid behaves in a similar way as concentrated sulphuric (VI) acid?
Answers to Questions 5.3.2(a) 
- (a) With sulphur: Sulphur dissolves in hot concentrated sulphuric (VI) acid, with effervescence. An acidic colourless
gas with a pungent smell is produced. The acid oxidizes sulphur to sulphur (IV) oxide, while it is itself reduced to water and sulphur (IV) oxide.
S(s) + 2H2SO4(l) → 2H2O(l) + 3SO2(g)
(b) With magnesium: Magnesium initially reacts slowly with concentrated sulphuric (VI) acid, but this speeds up as more water which enhances ionic dissociation of the acid is produced. An acidic colourless gas with a pungent smell is released. The gas is sulphur (VI) oxide, produced as the acid is reduced and magnesium metal is oxidized to magnesium ions.
Mg(s) + 2H2SO4(l) → MgSO4(aq) + 2H2O(l) + SO2(g)
The reaction is slow because concentrated sulphuric (VI) acid is weak, only partially dissociated into ions.
(c) With copper: Copper metal reacts fairly vigorously with concentrated sulphuric (IV) acid, producing a blue solution and an acidic colourless gas that has a pungent smell. The gas is sulphur (IV) oxide, produced as the acid oxidizes copper metal to copper ions, and it is itself reduced to water and sulphur (IV) oxide. Although copper is less reactive than hydrogen, it reacts with concentrated sulphuric (IV) acid because the latter reacts, not through hydrogen ions as is typical of acids, but as an oxidizer.
Cu(s) + 2H2SO4(l) → CuSO4(aq) + 2H2O(l) + SO2(g)
(d) With carbon: Carbon reacts with hot concentrated sulphuric (VI) acid to produce colourless gases. That is because carbon is oxidized to carbon (IV) oxide, and the acid is reduced to sulphur (IV) oxide and water.
C(s) + 2H2SO4(l) → 2H2O(l) + 2SO2(g) + CO2(g) - (a) Metal + Concentrated sulphuric (VI) acid → Metal sulphate + Sulphur (IV) oxide + Water
(b) Non-metal + Concentrated sulphuric (VI) acid → Water + Sulphur (IV) oxide + Non-metal oxide - It is a strong oxidizer, strong dehydrating agent, and has both covalent (oily) and polar bond characters.
- Concentrated nitric (V) acid.