Chromium (VI) forms two different oxyanions, the orange dichromate ion, Cr2o72-, And the yellow chromate ion, CrO4 2-. The equilibrium reaction between the ions is: Cr2O7 2- (aq) + H2O(l)→ 2CrO4 2-(aq) + 2H(aq)
Explain
a) Why does the orange dichromate solution turn yellow when sodium hydroxide is added. Write the net ionic equation for this shift.
b) How will this system shift at equilibrium if the temperature is increased

See explanation

Explanation:

Let us look at the reaction again;

Cr2O7 2- (aq) + H2O(l)⇄ 2CrO4 2-(aq) + 2H^+(aq)

When we add sodium hydroxide to the system as shown, the hydroxide ion removes the hydrogen ion thereby leaving a large concentration CrO4^2-(aq) in the system this causes the solution to turn green(equilibrium position shifts to the right).

The net ionic equation is;

OH^-(aq) + H^+(aq) > H2O(l)

The reaction;

OH^-(aq) + H^+(aq) > H2O(l) is exothermic hence, if the temperature of the system is increased, the equilibrium position will shift towards the left hand side and the solution turns orange.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.