Most-appropriate topic codes (Cambridge IGCSE Chemistry 0620):
• Topic 7.3 — Preparation of salts
• Topic 8.4 — Transition elements
(a)(i)
$$Pb^{2+}(aq) + SO_{4}^{2-}(aq) \rightarrow PbSO_{4}(s)$$
(a)(ii) Lead(II) nitrate. (General solubility rules state that all nitrate salts are soluble in water, making it the perfect standard reagent to provide aqueous metal ions).
(a)(iii) Sodium sulfate (or potassium sulfate / ammonium sulfate). (Group I salts and ammonium salts are universally soluble).
(a)(iv) Residue.
(a)(v) Wash the precipitate on the filter paper with distilled water (to remove any soluble impurities), and then use a suitable method of drying, such as pressing it between clean filter papers or placing it in a warm drying oven.
(b)(i) Similarities to Group I (Any two):
1. It has good electrical conductivity.
2. It forms soluble salts.
3. It forms basic oxides.
(b)(ii) Differences from Group I (Any two):
1. It has variable oxidation states (e.g., $Cu^{+}$ and $Cu^{2+}$ whereas Group I is strictly $+1$).
2. It forms coloured compounds (Group I compounds are typically white/colourless).
3. It acts as a catalyst.
