Suppose you have an aqueous solution prepared by dissolving 0.051 mol of NaH2PO4 in 1 L of water (pK, (H2P04¯) = 7.21). This solution is not a buffer, but suppose you want to make it into one. How many moles of solid NaH2 PO4 must you add to this aqueous solution to make it into: a. A buffer of pH 7.21 n = mol b. A buffer of pH 6.21 mol c. A buffer of pH 8.21 n = mol

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Ka(HOAC) = 1.8 x 10-5. A 1-L buffer solution is prepared by mixing 0.35 mol HOAC and 0.45 mol NaOAc. Which of the following processes will increase the pH of the above buffer solution? O a. add more water b.add more HOA c. add some HCI into the above buffer SO d. add some NH3 into the above buffer e. None of the above

5. A common buffer solution can be prepared by using ammonia and ammonium salts. The base equilibrium constant is 1.815×10-5. A student is preparing a pH buffer solution with 2.561 M NH3 solution and (NH4)2SO4 solid. Please answer the following questions. A. B. What is the best pH buffer range of the buffer solution that can be prepared by NH3 solution and (NH4)2SO4 solid? Please put down "1" if the answer is pH = 4.741 ± 1, please put down "2" if the answer is pH = 4.741 ± 10, please put down "3" if the answer is pH = 9.26 ± 1, please put down "4" if the answer is pH = 9.26 ± 10. Your answer follows. Assume that the addition of the solid will NOT change the volume, how many grams of is needed to prepare a pH = 8.66 buffer solution? The volume of the buffer solution is 250.0 mL. grams

7. A solution was made by mixing 50.0 mL of 0.750 M HCN with 25.0 mL of water. What is the pH of this solution? The pka of HCN = 9.31. 8. One of the compounds featured on the TV series "Breaking Bad" was hydrofluoric acid (HF), pKa = 3.14. a) A solution of HF has a pH = 1.77. What was the initial [HF] for this solution in mol L-1? b) What is the equilibrium concentration of F in this solution in mol L-1? c) What is the percent ionization of HF in this solution?