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CHM 2046Quiz 2ASpring2005

CHM 2046Quiz 2ASpring2005 - KCl NaBr NaH 2 PO 4 NaF KNO 2(2...

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CHM 2046 Quiz 2A Spring, 2005 Answer all questions. Be careful to give your final answer to the correct significant figures. Assume all temperatures are 25 H C. 1. a) (3 points)    NH 2 Me is a weak base.  Write down the base dissociation (base ionization) equation for NH 2 Me in  water. b) (2 points)    Complete the expression for the base-dissociation constant (K b ) for NH 2 Me. K b  =  c) (8 points) Calculate the pH of a 0.40 M solution of NH 2 Me (K b  = 4.4 x 10 -4 ). 2. a) (3 points) The K a  of benzoic acid (C 6 H 5 COOH) is 6.3 x 10 -5 .  What is the K b  of its conjugate base, benzoate  (C 6 H 5 COO - )? b) (2 points) Which one of the following salts will give a basic solution when dissolved in water?  Circle your choice. CaCl 2 , NH 2 Et 2 Cl, KF, NaNO 3 , KI (2 points) Write an equation for the reaction that occurs when the salt dissolves in water and makes the solution  basic. c) (2 points) Which one of the following salts will give an acidic solution when dissolved in water?  Circle your choice.
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Unformatted text preview: KCl, NaBr, NaH 2 PO 4 , NaF, KNO 2 (2 points) Write an equation for the reaction that occurs when the salt dissolves in water and makes the solution basic. 3. a) (10 points) What is the pH of a buffer solution prepared from adding 60.0 mL of 0.22 M nitrous acid (HNO 2 ) solution to 50.0 mL of 0.24 M sodium nitrite (NaNO 2 ) solution? (K a for HNO 2 is 7.1 x 10-4 ). b) (10 points) What is the new pH if 10.0 mL of a 0.20 M solution of NaOH is added? 4. Will a solution of the salt NH 4 F be acidic, neutral or basic? (K a for HF is 6.8 x 10-4 , and K b for NH 3 is 1.8 x 10-5 ) a) (1 point) Write your answer here: The solution will be ________________________ b) (5 points) Explain how you reached your answer....
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CHM 2046Quiz 2ASpring2005 - KCl NaBr NaH 2 PO 4 NaF KNO 2(2...

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