Question

Aqueous chromate ion, CrO4
2-, exists in equilibrium with aqueous dichromate ion, Cr2O7
2- in acidic solution. What effect will (i) increasing the dichromate ion, and (ii) adding HCl
have on the equilibrium?

Answer 1

Solution.

We write chemical equilibrium equation:

$2CrO4^{2-} + 2H3O^+ = Cr2O7^{2-} + 3H2O$

To solve this task, we must use Le Chatelier rule.

(i)

An increase in the concentration of the dichromate ion shifts the chemical equilibrium towards the starting materials (to the left).

(ii)

The addition of hydrochloric acid shifts the chemical equilibrium towards the formation of reaction products (to the right).

Answer:

(i)

An increase in the concentration of the dichromate ion shifts the chemical equilibrium towards the starting materials (to the left).

(ii)

The addition of hydrochloric acid shifts the chemical equilibrium towards the formation of reaction products (to the right).