2010-03-01 - Problem Set _11 - Polyprotic Acids and Bases & Autoprotolysis and pH

2010-03-01 - Problem Set _11 - Polyprotic Acids and Bases & Autoprotolysis and pH

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Problem Set #11 – Polyprotic Acids and Bases & Autoprotolysis and pH Refer to Tables 10.9 in your notes for needed K a values. 1. Write the stepwise proton transfer equilibria for the deprotonation of H 3 AsO 4 . 2. Calculate the pH of 0.15 M H 2 SO 4 (aq) at 25° C. 3. Estimate the pH of (a) 0.15 M NaHSO 3 (aq) and (b) 0.050 M NaHSO 3 (aq). 4. State which species (H 2 A, HA - , or A 2 - ) you expect to be the form present in highest concentration in aqueous solution at pH = 6.50 for the acids (a) phosphorous acid, (b) oxalic acid, and (c) hydrosulfuric acid 5. Calculate the pH of (a) 6.55 x 10 -7 M HClO 4 (aq) and (b) 9.78 x 10 -8 M KOH. 6. Calculate the concentrations of H 2 CO 3 , HCO 3 - , CO 3 2- , H 3 O + , and OH - present in 0.0456 M H 2 CO 3 (aq). 7. Calculate the concentrations of H 2 CO 3 , HCO 3 - , CO 3 2- , H 3 O + , and OH - present in 0.0456 M Na 2 CO 3 (aq). 8. Calculate the pH of 0.20 M H 2 S, ignoring the second deprotonation only if justified. 9. Calculate the pH of 1.00 x 10 -6 M HBrO(aq).
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Unformatted text preview: 10. Citric acid, which is extracted from citrus fruits and pineapples, undergoes three successive deprotonations with pKa values of 3.14, 5.95, and 6.39. Estimate the pH of (a) a 0.15 M aqueous solution of the monosodium salt and (b) a 0.075 M aqueous solution of the disodium salt. 11. A large volume of 0.150 M H 2 SO 3 (aq) is treated with a solid, strong base to adjust the pH to 5.50. Assume that the addition of the base does not significantly affect the volume of the solution. Estimate the concentrations of H 2 SO 3 , HSO 3-, and SO 3 2-present in the final solution. 12. Calculate the pH of 0.015 M H 3 PO 4 (aq), ignoring the second deprotonation only if justified. 13. Compute the concentration of the phosphate species in a H 3 PO 4 solution that has pH = 2.25, if the total concentration of all four forms of the dissolved phosphates is 1.5 x 10-2 molL-1 ....
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This note was uploaded on 03/01/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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