24.4 Ligand Substitution Of Chromium (III) Ions

Question 1

Reaction with water Cr

Answer 1

1. Chromium potassium sulfate (CHROME ALUM) forms a PALE PURPLE SOLUTION when dissolved in water.

KCr(SO4)2*12(H2O) -> [Cr(H2O)6]3+(aq)

2. Chromium (III) sulfate dissolved in water to form a GREEN solution.

Cr2(SO4)3 + 5H2O-> [Cr(H2O)5SO4]

Question 2

Reaction with excess of aqueous ammonia Cr

Answer 2

1. A GREY-GREEN PRECIPITATE of Cu(OH)3 first forms.

Cr3+ + 3OH- -> Cu(OH)3

2. This precipitate then dissolves in excess ammonia to form a PURPLE solution of [Cr(NH3)6]3+.

[Cr(H2O)6]3+(aq) + 6NH3(aq) -> [Cr(NH3)6]3+(aq) + 6H2O(l)