Metal Reactivity and Compound Stability

Steps:

• Recall reactivity series: metals like Ca, Mg, Al react with water/acids based on position.
• Check thermal decomposition: stability of carbonates increases down groups.
• Evaluate extraction methods: less reactive metals use carbon reduction if oxide is reducible.
• Test acid reactions: amphoteric metals like Al dissolve in dilute acids.

Why D is correct:

• Aluminium is above hydrogen in reactivity series, so pure Al reacts with dilute HCl per equation: 2Al + 6HCl → 2AlCl₃ + 3H₂.

Why the others are wrong:

• A: Calcium reacts with both cold water and steam, producing hydrogen and hydroxide/oxide.
• B: Zinc carbonate decomposes at lower temperature (~140°C) than lead carbonate (~300°C) due to decreasing charge density.
• C: MgO is too stable for carbon reduction; magnesium is extracted by electrolysis of molten MgCl₂.

Final answer: D