Predict what would happen if the ammonium system described in the experiment was heated.

Answer is: concentration of products increases (ammonia nad water).

Chemical reaction: heat + NH₄⁺ + OH⁻ ⇄ NH₃ + H₂ O.

According to Le Chatelier's Principle, the position of equilibrium moves to counteract the change, because heat is increased, system consume that heat, so equilibrium is shifted to right, by decreasing concentration of reaactants and increasing concentration of product.