Question

Why iron(III) solutions are more soluble in acidic solutions using Le Chatalier's principle?

Answer 1

First, denote the equations:

Fe3+(aq) + H2O(l)

there might be equilbirium:

Fe3+(aq) + 3H2O(l) <--> Fe(OH)3(s) + 3H+(aq)

therefore

let FeX3 be a generic salt which is not that soluble

FeX3(s) = Fe+3 + 3X-

in solution

Note that Fe3+ forms equilbirium with water, so Fe(OH)3 precipitates.... therefore, Fe+3 decreases in solution

according to Le Chatalier's principle

The statement is as follows:

If any equilibrium is disturbed, that is, change in conditions such as P,T, concentration, partial pressure, etc.., the system will counterbalance such change in order to favour the system's equilbirium.

• Change in concentration
• Change in pressure
• Change in temperature

We are decreasing Fe+3

so

the shift in:

FeX3(s) = Fe+3 + 3X-

favours more FeX3(s) going into solution as Fe+3 and 3X- in order to counterbalance the loss of Fe+3 ions in Fe(OH)3(S)