1.0 L of buffer holds 0.10 mol HA and 0.10 mol NaA (no volume change on additions). Select the correct statements.

AAdding 0.01 mol NaOH raises pH by less than 0.1 unit
BAdding 0.01 mol HCl lowers pH by about 0.09 unit
CAdding 0.05 mol NaOH raises pH by about 0.48 unit
DAdding 0.01 mol solid NaA raises pH by about 0.09 unit

Answer: A, B, C

0.01 mol NaOH: log(0.11/0.09) = 0.087 (a, b true: HCl gives the same magnitude downward). 0.05 mol NaOH: log(0.15/0.05) = 0.477 (c true). 0.01 mol NaA: log(0.11/0.10) = 0.041, only 0.04 (d false).

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