Question

Sulphide ion is soft base and its ores are common for metals.
(a) Pb (b) Al (c) Ag (d) Mg

• (a) and (c) only
• (a) and (d) only
• (a) and (b) only
• (c) and (d) only

Hint:

By the HSAB principle, soft \(S^{2-}\) pairs with soft acids such as \(Pb^{2+}\) and \(Ag^+\); hard \(Al^{3+}\) and \(Mg^{2+}\) occur as oxides, carbonates and halides.

Answer 1

The Correct Option is A

Soft bases prefer soft acids. \(Pb^{2+}\) and \(Ag^{+}\) are soft acids, so they occur as sulphide ores (galena PbS, argentite \(Ag_2S\)).
\(Al^{3+}\) and \(Mg^{2+}\) are hard acids, preferring hard bases like \(O^{2-}\), \(CO_3^{2-}\), \(Cl^-\): bauxite, magnesite, carnallite etc.
So the metals with common sulphide ores are Pb and Ag: (a) and (c) only.
Answer: (1) (a) and (c) only