Solutions to Chapter 1 Q11,12

Solutions to Chapter 1 Q11,12 - 1.62= [ H 2 PO 4-]/[HPO 4...

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11. H 2 PO 4 - HPO 4 2- with a pKa of 7.21 (a) pH = pKa + log[A-]/[HA] @ pH 7 What is the ratio of H 2 PO 4 - /HPO 4 2- ? [A-] = [HPO 4 2- ] [HA] = [H 2 PO 4 - ] pH = pKa + log ([HPO 4 2- ]/[ H 2 PO 4 - ]) pH - pKa = log ([HPO 4 2- ]/[ H 2 PO 4 - ]) 10^ (pH-pKa) = ([HPO 4 2- ]/[ H 2 PO 4 - ]) 10^ (7-7.21) = ([HPO 4 2- ]/[ H 2 PO 4 - ]) 0.616 = ([HPO 4 2- ]/[ H 2 PO 4 - ]) 1/(0.616) =
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Unformatted text preview: 1.62= [ H 2 PO 4-]/[HPO 4 2-] 12. Use the Henderson-Hasselbach Equation: pH = pKa + log([A-]/[HA]) The pKa of acetate = 4.75 [A-] = [Acetate] [HCl] [HA] = [HCl] pH = 4.75+log([0.1-0.0025]/[0.0025])=4.75+1.59 = 6.34...
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