17. Acid and Base Equilibrium

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Multiple Choice

Determine the pOH of 0.450 M citric acid, H₃C₆H₅O₇. It possesses K_a1 = 7.4 × 10⁻⁴, K_a2 = 1.7 × 10⁻⁵ and K_a3 = 4.0 × 10⁻⁷.

Calculate the [H3O+] and pH of each polyprotic acid solution. a. 0.350 M H3PO4

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A 40.0 mL sample of a mixture of HCl and H3PO4 was titrated with 0.100 M NaOH. The first equivalence point was reached after 88.0 mL of base, and the second equivalence point was reached after 126.4 mL of base.

(e) Sketch the pH titration curve, and label the buffer regions and equivalence points.

The acidity of lemon juice is derived primarily from citric acid (H3Cit), a triprotic acid. What are the concentrations of H3Cit, H2Cit-, HCit2-, and Cit3- in a sample of lemon juice that has a pH of 2.37 and a total concentration of the four citrate-containing species of 0.350 M? <IMAGE>

Citric acid, which is present in citrus fruits, is a triprotic acid (Table 16.3). (a) Calculate the pH of a 0.040 M solution of citric acid. (b) Did you have to make any approximations or assumptions in completing your calculations? (c) Is the concentration of citrate ion 1C6H5O7 3-2 equal to, less than, or greater than the H+ ion concentration?

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A 7.0 mass % solution of H3PO4 in water has a density of 1.0353 g/mL. Calculate the pH and the molar concentrations of all species present (H3PO4, H2PO4-, PO43-, H3O+ , and OH-) in the solution. Values of equilibrium constants are listed in Appendix C.

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