Question

At a concentration of 1 M, the weak acid HNO2 is 2% ionized and the pH of the solution is 1.7. What happens when KNO2(s) is dissolved into the solution?

Answer 1

When the nitrous acid is dissolved in water, the following equilibrium is established:\[HNO_2(aq)+H_2O(l) \rightleftharpoons NO_2^-(aq)+H_3O^+(aq)\]When more nitrite is added to the solution, the reaction will shift towards the reactants because of La Châtelier's principle. In doing this, the solution will decrease in hydronium concentration and therefore the pH will increase by some amount.

Another way to look at this is that since nitrite is the conjugate base of nitrous acid, when it is introduced into a solution of water, it will act as a base and take protons from the hydronium.

Answer 2

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