Question

How many moles of H2 P O4 1- and HPO4 2- would be needed to prepare 1.0 L of a 0.01 M phosphate buffer with a pH of 7.15? (H2 P O4 1- ßà HPO4 2- pKa = 6.86)

Answer 1

To prepare a phosphate buffer with a pH of 7.15, we can use the Henderson-Hasselbalch equation to calculate the ratio of [A-] to [HA].

Step-by-step explanation:

To prepare a phosphate buffer with a pH of 7.15, we need to calculate the amounts of H2PO4- and HPO4^2- needed. The Henderson-Hasselbalch equation is used for buffer calculations:

pH = pKa + log([A-]/[HA])

Given pKa = 6.86, pH = 7.15, and the total buffer volume is 1.0 L, we can calculate the ratio [A-]/[HA] using the Henderson-Hasselbalch equation. From the equation, we know that [A-]/[HA] = 10^(pH - pKa).

Substituting the values, we get 10^(7.15 - 6.86) = 1.848