In the first trial, when we add HCl to the solution, it fully dissolves into H ⁺ and Cl ^- . By increasing the concentration of Cl ^- ions in the solution, the equilibrium shifts to the right to compensate.

When we add H₂O in the second trial, we increase the concentration of products. In response, the equilibrium shifts to the left side of the equation.

When we increase the temperature of the solution in the third trial, we must consider the enthalpy of the reaction. Because this reaction is endothermic, heat can be considered to exist on the products side of the equation. Therefore, by increasing the temperature, the equilibrium shifts to the left (reactants) in accordance with Le Chatelier's Principle.