Chemistry

Chemistry

Problem

Calculate the composition of an acidic buffer solution made up of HA and NaA of total molarity 0.29 having pH = 4.4 and Ka=1.8×10−5K_a = 1.8 \times 10^{-5} .
Intuitive explanation

A buffer works because the ratio of conjugate base to weak acid determines pH through the Henderson–Hasselbalch equation. Your job is to use the given pH and KaK_a to find what fraction must be A−A^- versus HAHA, then scale those fractions by the total molarity to get actual concentrations. The key insight is that pH directly constrains the [A−]/[HA][A^-]/[HA] ratio—once you know that ratio and the sum [HA]+[A−]=0.29[HA] + [A^-] = 0.29 M, you can solve for both individually.

Intuitive explanation

A buffer works because the ratio of conjugate base to weak acid determines pH through the Henderson–Hasselbalch equation. Your job is to use the given pH and KaK_a to find what fraction must be A−A^- versus HAHA, then scale those fractions by the total molarity to get actual concentrations. The key insight is that pH directly constrains the [A−]/[HA][A^-]/[HA] ratio—once you know that ratio and the sum [HA]+[A−]=0.29[HA] + [A^-] = 0.29 M, you can solve for both individually.

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