A Solution Is Prepared by Dissolving 0

Multiple Choice

A solution is prepared by dissolving 0.23 mol of nitrous acid and 0.27 mol of sodium nitrite in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly. The pH does not decrease drastically because the HCl reacts with the ________ present in the buffer solution. The K_a of nitrous acid is 1.36 × 10^-3.

A) H₂O
B) H₃O⁺
C) nitrite ion
D) nitrous acid
E) This is a buffer solution: the pH does not change at all upon addition of acid or base.