Ammonium Chloride (NH4Cl) is added to an aqueous solution of Ammonia containing phenolphthalein indicator. Phenolphthalein is pink in the presence of OH- ions, but clear otherwise.
When Ammonia (NH3) is dissolved in water, it forms the following equilibrium system:
NH3(g) + H2O(l) Ⅴ NH4+(aq) + OH-(aq)
Using Le Chatelier's principle, explain why the addition of NH4Cl causes the solution to turn clear.