Two monoprotic weak acids, HX and HY

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

Problem

Two monoprotic weak acids, HX and HY, are each titrated separately with 0.100 M NaOH until the equivalence point is reached. Both titrations begin with 25.0 mL of 0.100 M acid. The dissociation constants are Ka,HX=1.0×10−5K_{a,\text{HX}} = 1.0 \times 10^{-5} and Ka,HY=1.0×10−7K_{a,\text{HY}} = 1.0 \times 10^{-7}. Which of the following best describes the relationship between the equivalence-point pH values, pHeq\text{pH}_{\text{eq}}, of the two titrations? (a) pHeq(HX) = pHeq(HY)\text{pH}_{\text{eq}}(\text{HX}) \, = \, \text{pH}_{\text{eq}}(\text{HY}) (b) pHeq(HY) > pHeq(HX)\text{pH}_{\text{eq}}(\text{HY}) \, > \, \text{pH}_{\text{eq}}(\text{HX}) (c) pHeq(HX) > pHeq(HY)\text{pH}_{\text{eq}}(\text{HX}) \, > \, \text{pH}_{\text{eq}}(\text{HY}) (d) The relative values cannot be predicted without additional data.

Related theory

Browse the problem library