Question

For a buffer solution made of 0.500M sodium acetate and 0.0500M acetic acid, the pH would be? The Ka of acetic acid is 1.7×10−⁵.

a. 4.98
b. 5.77
c. 2.66
d. 4.77
e. 3.75

Answer 1

The pH of the buffer solution made from 0.500M sodium acetate and 0.0500M acetic acid is 5.77, calculated using the Henderson-Hasselbalch equation with the given concentrations and the Ka value for acetic acid.

Step-by-step explanation:

To calculate the pH of a buffer solution made from 0.500M sodium acetate (NaCH3CO2) and 0.0500M acetic acid (CH3COOH), we can use the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

Where pKa is the negative logarithm of the acid dissociation constant (Ka), [A-] is the concentration of the acetate ion, and [HA] is the concentration of acetic acid.

Since the Ka of acetic acid is 1.7×10−5, we first calculate the pKa:

pKa = -log(Ka) = -log(1.7×10−5) ≈ 4.77

Now we apply the Henderson-Hasselbalch equation:

pH = 4.77 + log(0.500 / 0.0500) = 4.77 + log(10) = 4.77 + 1 = 5.77

Thus, the pH of the buffer solution would be 5.77 (option b).