Question

Solve for the pH of a buffer solution using the Henderson-Hasselbalch equation that is (pg. 309).

A 1.0 L solution of 0.32 M HNO2 and 0.20 M NO₂²⁻ constitutes a buffer solution. The Ka of HNO2 is 6.8 x 10⁻⁴.
HINT: A is the concentration of the conjugate base and HA is the concentration of the weak acid. Do not forget to convert Ka to pKa.

Answer 1

To calculate the pH of a buffer solution containing 0.32 M HNO2 and 0.20 M NO2⁻, use the Henderson-Hasselbalch equation. After converting Ka to pKa, plug in the values and solve to find that the pH of the buffer solution is 2.97.

Step-by-step explanation:

To solve for the pH of the buffer solution using the Henderson-Hasselbalch equation, first convert the Ka of HNO2 to pKa. The pKa is the negative logarithm of Ka.

pKa = -log(Ka) = -log(6.8 x 10⁻⁴) = 3.17

Now apply the Henderson-Hasselbalch equation:

pH = pKa + log(A⁻ / HA)

Where A⁻ represents the concentration of the conjugate base (NO₂⁻⁻) and HA represents the concentration of the weak acid (HNO2).

pH = 3.17 + log(0.20 / 0.32)

pH = 3.17 + log(0.625)

pH = 3.17 + (-0.204)

pH = 2.97

The pH of the buffer solution is 2.97.