Exam3AKey

Exam3AKey - 1) a) (25) How many grams of NaBrO (Mm = 118.9...

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1) a) (25) How many grams of NaBrO (M m = 118.9 g/mol) must be added to 455 mL of a 1.027 M solution of HBrO in order to prepare a pH = 8.50 buffer? experiment starts with 455 mL x 1.027 M = 467 mmol acid pH = pK a + log acid base 8.50 = 8.70 + log 467 base -0.20 = log 467 base 467 base = 10 -0.20 = 0.631 base = 295 mmol 0.295 mol x 118.9 g/mol = 35.1 g b) (22) A second 455 mL sample of HBrO/NaBrO solution contains 1.027 M of each. 100.0 mL of 2.00 M HCl is added to this second solution. What is the pH change for this second solution? start with : 467 mmol HBrO 467 mmol BrO 1- 100.0 mL x 2.00 M = 200. mmol H 3 O 1+ BrO 1- + H 3 O 1+ ¾ HBrO + H 2 O i 467 200 467 mmol -200 -200 + 200 mmol e 267 0 667 mmol pH = pK a + log acid base = 8.70 + log 667 267 = 8.30 pH = 8.30 – 8.70 = pH = -0.40 2) (18) Indicate whether each of the following aqueous solutions would be acidic, basic or neutral NaNO 3 NaHS H 2 C 2 O 4 neutral basic acidic
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3) A solution is labeled 0.250 M NaCN(aq).
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Exam3AKey - 1) a) (25) How many grams of NaBrO (Mm = 118.9...

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