Question

Right balance net ionic equation describing each of the following reactions:
a)the confirming test for tin
b)the confirming test for copper

Answer 1

a) For the first reaction Iron reduces Sn⁺⁴ to Sn⁺²:
Sn⁴⁺(aq) + Fe(s) → Sn²⁺(aq) + Fe²⁺(aq)

Then by addition of HgCl₂, a white precipitate of Hg₂Cl₂ is formed

Sn²⁺(aq) + 2HgCl₂(aq) → Sn⁴⁺(aq) + Hg₂Cl₂(s) + 2Cl^-(aq)

When there is a lot of Sn⁺⁴ converted to Sn⁺², the Hg₂Cl₂ produced above continues to be reduced to Mercury metal:
Sn²⁺(aq) + Hg₂Cl₂(s) → Sn⁴⁺(aq) + 2Hg(l) + 2Cl^-(aq)

b) To 10 drops of solution, add 0.5 M K₄Fe(CN)₆ dropwise until a red-brown precipitate forms.

2 Cu²⁺ + K₄Fe(CN)₆ Cu₂Fe(CN)₆ + 4 K⁺

2 Cu²⁺ + Fe(CN)₆^4- Cu₂Fe(CN)₆