At a pH of 7.40, what is the ratio of the molar concentrations of POto HPO2 Expr

Question

At a pH of 7.40, what is the ratio of the molar concentrations of POto HPO2 Express your answer using two significant figures. View Available Hint(s) PO, Part B to H2PO4? At a pH of 7.40, what is the ratio of the molar concentrations of HPO4 Express your answer using two significant figures. View Available Hint(s) - Part C At a pH of 7.40, what is the ratio of the molar concentrations of H2PO4 to H3P04? Express your answer using two significant figures. View Available Hint(s) Part D At a pH of 7.40, what is the ratio of the molar concentrations of COsto HC? Express your answer using two significant figures. View Available Hint(s)

Explanation / Answer

A.

pKa of HPO42- = 12.35

Formula,

pH = pKa + Log[salt]/[acid]

7.40 = 12.35 + Log[PO43-]/[HPO42-]

Log[PO43-]/[HPO42-] = - 4.95

[PO43-] / [HPO42-] = 1.12 * 10-5

B.

pKa of H2PO4- = 7.20

So,

7.40 = 7.20 + Log[HPO42-]/[H2PO4-]

[PO42-] / [H2PO4-] = 1.58

C.

pKa of H3PO4 = 2.15

7.40 = 2.15 + Log[H2PO4-]/[H3PO4]

[H2PO4-] / [H3PO4] = 1.78 * 105

D.

pKa of HCO3- = 10.33

7.40 = 10.33 + Log[CO32-] / [HCO3-]

[CO32-] / [HCO3-] = 1.17 * 10-3

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