Two buffer solutions at the same temperature contain the weak acid ( HB ) and its…

CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases

Problem

Two 1.0 L1.0\,\text{L} buffer solutions at the same temperature contain the weak acid HB\text{HB} and its conjugate base B−\text{B}^-. Data for each buffer are given below. Buffer X: [HB]=0.20 M,  [B−]=0.20 M[\text{HB}]=0.20\,\text{M},\;[\text{B}^-]=0.20\,\text{M} Buffer Y: [HB]=0.05 M,  [B−]=0.50 M[\text{HB}]=0.05\,\text{M},\;[\text{B}^-]=0.50\,\text{M} Which statement correctly compares their abilities to resist a pH decrease upon addition of a strong acid? (a) Buffer X has the greater capacity because its components are equimolar. (b) Buffer X has the greater capacity because its higher concentration of HB\text{HB} better absorbs added acid. (c) Buffer Y has the greater capacity because it contains more B− \text{B}^- in total moles. (d) Both buffers have identical capacities because their overall solute concentrations are similar.

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