Question

Suppose you are assigned to prepare a buffer of 0.10M HNO2 (Ka=1.7 x 10^-4) and 0.10M NaNO2 by mixing equal volumes of both solutions. What is the pH of the resultant solution?

How would I first start this question? I have no clue what the steps are to be frank.

Answer 1

if the volumes of the weak acid and its conjugate base are equal than the pH=pka of the solution. You know this by looking at the Henderson–Hasselbalch equation.

pH=pka+log[A^-]/[HA]

Where

A^-=NaNO2
and
HA= HNO2

Since the concentrations are equal, the above equation becomes the following:


pH=pka+log[1]

The log of 1 is 0, so the equation becomes

pH=pka

Where

pka=-log[Ka]



You can do the rest.