Which combination may be used to prepare a buffer having a pH of 8.8? K_a= 7 × 10^-3 for H₃PO₄; 8 × 10^-8 for H₂PO₄^-; 5 × 10^-13 for HPO₄^2- A) NaH₂PO₄ only B) NaH₂PO₄ and Na₂HPO₄ C) Na₃PO₄ and Na₂HPO₄ D) NaHPO₄ and H₃PO₄ E) H₃PO₄ and Na₃PO₄

Question

Quizplus · Accepted Answer

The combination of NaHS and Na2S can be used to prepare a buffer with a pH of around 8.8. The pKa values of HS- and S2- are 7.0 and 12.9, respectively. By mixing both the conjugate acid/base pairs, we can get a buffer solution with a pH near the pKa of the two ions, which is around 8.8. Therefore, the best choice is B, which includes NaHS and Na2S, two salts that can form a buffer solution with the desired pH. The other options do not provide a suitable combination of conjugate acid/base pairs.

Which Combination May Be Used to Prepare a Buffer Having