In: Chemistry
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(l) ⇌ CN-(aq) + H3O+ (aq) pH
after the concentration of HCN is increased
after the concentration of CN is decreased
HCN (aq) | H2O (l) | CN- (aq) | H3O+ (aq) | pH | ||
after the concentration of HCN is increased | no change | |||||
after the concentration of CN- is decreased | no change |
Explanation
According to Le Chatelier's principle, when an already established equilibrium is disturbed due to addition of a factor, the equilibrium will shift in that direction which minimizes the effect of that addition.
In first case, concentration of HCN is increased. The system moves towards products to decrease the concentration of HCN and reestablish equilibrium. This means there will be increase in the H3O+ concentration and pH will decrease.
In second case, concentration of CN- is decreased. The system moves towards products to increase the concentration of CN- and reestablish equilibrium. This means there will be increase in the H3O+ concentration and pH will decrease.