Question

Indicate how the concentration of each aqueous species in the chemical equation changes to reestablish equilibrium after changing the concentration of a reactant or product. Also indicate how the pH changes. An up arrow indicates an increase in concentration, a down arrow indicates a decrease in concentration, and leaving it blank means there is no change in the concentration.

HCN(aq) +H₂O(1) = CN-(aq) + H, 0+ (aq) pH
after the concentration of HCN is increased
after the concentration of CN is decreased

Answer 1

Increasing the concentration of HCN shifts the equilibrium right, increasing H+ and CN- concentrations and decreasing pH. Decreasing CN- concentration also shifts the equilibrium right, increasing H+ concentration and decreasing pH.

Step-by-step explanation:

When the concentration of HCN is increased in an equilibrium system, the system will respond according to Le Chatelier's Principle, which states that the system will adjust to minimize the change. This results in a shift of the equilibrium toward the right, producing more products, assuming the reaction is: HCN(aq) ⇌ H+(aq) + CN-(aq). Therefore, increasing HCN causes an increase in H+ and CN- concentration. Conversely, when the concentration of CN- is decreased, the equilibrium will shift to the right to produce more CN- and H+ from HCN, thus increasing their concentrations.

As the system adjusts to these changes, the pH will also alter. An increase in H+ concentration will decrease the pH, making the solution more acidic. Conversely, a decrease in H+ concentration would increase the pH, making the solution more basic.