Question

A buffer solution is formed by mixing equal volumes of 0.12MNH3(aq) and 0.10MHCl(aq), which reduces the concentration of both solutions by one half. Based on the pKa data given in the table, which of the following gives the pH of the buffer solution?

A
pH=−log(0.050)=1.30
B
pH=9.25+log(0.010/0.050)=8.55
C
pH=9.25+log(0.060/0.050)=9.32
D
pH=14.00−(−log(0.010))=12.00

Answer 1

The correct answer is B.

The Henderson-Hasselbalch equation can be used to calculate the pH of a buffer solution:

pH = pKa + log([base]/[acid])

In this case, the pKa of ammonia is 9.25, the concentration of the base is 0.010 M, and the concentration of the acid is 0.050 M. Therefore, the pH of the buffer solution is:

pH = 9.25 + log(0.010/0.050) = 8.55

Step-by-step explanation: