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Unformatted text preview: Chemistry 5 Winter 2008 Exam #2 Practice Problems 1. Vitamin C is another name for ascorbic acid (HC 6 H 7 O 6 ; K a = 8.0 x 10-5 ). Determine the pH of a solution made by dissolving a 0.500 g tablet of vitamin C in 0.100 L of water. 2 . The sodium salt of the cacodylate anion, which is the conjugate base of cacodylic acid, has the formula NaO 2 As(CH 3 ) 2 . 3H 2 O and a molar mass of 214.02 g mol-1 . A solution is prepared by mixing 21.40 g of sodium cacodylate with enough water to make 1.000 L of solution. Then 50.00 mL of this solution is mixed with 29.55 mL of 0.100 M HCl and enough water to bring the total volume to 100.00 mL. The pH of this solution is found to be 6.00. From this result, determine the pK a of cacodylic acid. 3 . Starting with 0.500 L of 0.100 M formic acid (K a = 1.77 x 10-4 ) and a 0.0500 M NaOH solution, what volume of the NaOH solution needs to be added to the formic acid solution to prepare a pH 4.00 buffer solution. 4 . In the third week of lab we began using the ion exchange columns and were cautioned to make sure that all the Cu +2 ions were removed before adding NaOH; if not, then the black precipitate Cu(OH) 2 (K sp of 1.6 x 10-19 ) would form in the column. ) would form in the column....
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- Winter '08