試題詳解

5. The phosphate buffer system is maximally effective at a pH close to its pKa of 6.86. What is the pH of a mixture of 0.5 M NaH₂PO₄ and 0.05 M Na₂HPO₄?
(A) 5.86
(B) 6.86
(C) 7.19
(D) 7.86