Using Henderson–Hasselbalch, estimate the pH of a buffer solution containing 0.100 M acetic acid (HA) and 0.100 M sodium acetate (A−) with Ka = 1.8×10−5.

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Multiple Choice

Using Henderson–Hasselbalch, estimate the pH of a buffer solution containing 0.100 M acetic acid (HA) and 0.100 M sodium acetate (A−) with Ka = 1.8×10−5.

The pH of a buffer is given by Henderson–Hasselbalch: pH = pKa + log([A−]/[HA]). When the concentrations of the weak acid and its conjugate base are equal, the ratio [A−]/[HA] is 1, so the log term is zero and pH equals pKa. For acetic acid, pKa = -log10(Ka) = -log10(1.8×10−5) ≈ 4.74. Therefore, with equal amounts of HA and A−, the buffer’s pH is about 4.74. The proposed answer of around 7.00 would require a pH close to neutral, which would correspond to a pKa near 7 or a very different [A−]/[HA] ratio, not the equimolar case given. So the correct estimate is pH ≈ 4.74.

Using Henderson–Hasselbalch, estimate the pH of a buffer solution containing 0.100 M acetic acid (HA) and 0.100 M sodium acetate (A−) with Ka = 1.8×10−5.

Prepare for the NANTeL Chemistry Certification and Engineering Fundamentals Test with multiple choice questions, detailed explanations, and key insights to boost your understanding and confidence. Ace your exam!

Using Henderson–Hasselbalch, estimate the pH of a buffer solution containing 0.100 M acetic acid (HA) and 0.100 M sodium acetate (A−) with Ka = 1.8×10−5.

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