Question

Please work out all steps and do part a and b . Thanks :)

3. Phosphate buffers are important to regulating the pH of intracellular fluids at pH values generally between 7.1 and 7.2. (12 pts) a. What is the concentration ratio of HPO; to HPO. in intracellular fluid at pH 7.15? H2Pos(ag)HPO, (aq)(aq) K, - 62 x 10 b. Why is a buffer composed of HaPOs and H2PO ineffective in buffering the pH of intracellular fluid? H,PO4(aq)H2PO(aq)+H'(aq) K-7.5 x 103

Answer 1

a.) pH = -log[H+] so, [H+] = e^-7.15 = 7.079 x 10^-8 M

Now, H2PO4-(aq) <--> HPO42-(aq) + H+(aq)

Ka = [HPO42-][H+]/[H2PO4-]

[H2PO4-]/[HPO42-] = [H+]/Ka = 7.079 x 10^-8 M/6.2 x 10^-8 = 1.14

b.) We know, pH = pKa + log([base]/[acid])

Plug in some reasonable concentrations of base and acid (each between 0.01 and 1 M).
The pH is then between 0 and 4. These are approximations, but you can already see that the pH range is too low for the human body (where it should be much closer to 7)

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