Question

In which case pH will not change on dilution

• A. $0.01MCH_{3}COONa + 0.01MCH_{3}COOH$buffer
• B. $0.01MCH_{3}COONH_{4}$
• C. $0.01MNaH_{2}PO_{4}$
• D. In all cases

Answer 1

Answer: (D)

In all cases

Answer 2

Mixture of Sodium acetate and acetic acid is a buffer of pH value equal to pKa so its buffer capacity is maximum and hence its pH will not change signficiantly while CH3COONH4 is a salt of weak acid CH3COOH and weak base NH4OH whose magnitude of Ka and Kb are equal. So its pH does not depend upon concentration. Further more, NaH2PO4 is,in fact, a single solute buffer.