AP Chemistryeasymcq1 pt
In a buffer, doubling [A⁻] while holding [HA] constant changes the pH in which way?
A.It raises the pH by about 0.30 units
B.It lowers the pH by about 0.30 units
C.It leaves the pH unchanged
D.It doubles the pH
Explanation
Core Concept
Henderson-Hasselbalch gives pH = pKa + log([A⁻]/[HA]). Doubling the numerator multiplies the ratio by 2, and log 2 ≈ 0.30, so the pH rises by about 0.30 units. Enriching the basic partner nudges the buffer toward the basic side, exactly as the logarithm predicts.
Correct Answer
AIt raises the pH by about 0.30 units
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