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# hw4 - amg2845 hw04 McCord(53580 This print-out should have...

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amg2845 – hw04 – McCord – (53580) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points What is the hydroxide concentration [OH ] in an aqueous solution in which the hydronium ion concentration [H 3 O + ] is 1 × 10 5 M? 1. 1 × 10 5 M 2. 1 × 10 9 M correct 3. 1 × 10 14 M 4. 1 × 10 7 M Explanation: [H 3 O + ] = 1 × 10 5 M K w = [H 3 O + ][OH ] = 1 . 0 × 10 14 [OH ] = K w [H 3 O + ] = 1 . 0 × 10 14 1 × 10 5 = 1 × 10 9 M 002 10.0 points Which of the following is true in pure water at any temperature? 1. pH = 7.0 or greater than 7.0 2. [H 3 O + ][OH ] = 1.0 × 10 14 3. pH = 7.0 4. [H 3 O + ] = [OH ] correct 5. K w decreases with increasing tempera- ture. Explanation: K w is shown to INCREASE with increas- ing temperature. pH = 7 is only true when water is at 24 C. [H 3 O + ][OH ] = K w , which increases with temperature. At high temperatures pH can be less than 7. Thus [H 3 O + ] = [OH ] is the only case that is true. 003 10.0 points What is [H 3 O + ] when [OH ] = 3 . 3 × 10 9 M? 1. 3 . 3 × 10 9 M 2. 3 . 0 × 10 6 M correct 3. 1 . 0 × 10 7 M 4. 3 . 3 × 10 5 M 5. 6 . 6 × 10 5 M Explanation: [OH ] = 3 . 3 × 10 9 M K w = [H 3 O + ][OH ] = 1 × 10 14 [H 3 O + ] = K w [OH ] = 1 . 0 × 10 14 3 . 3 × 10 9 = 3 . 0 × 10 6 M 004 10.0 points What is [OH ] when [H 3 O + ] = 8 . 2 × 10 5 M? 1. 1 . 2 × 10 10 M correct 2. 1 . 2 × 10 4 M 3. 6 . 3 × 10 9 M 4. 8 . 2 × 10 5 M 5. 1 . 0 × 10 7 M Explanation: [H 3 O + ] = 8 . 2 × 10 5 M K w = [OH ][H 3 O + ] = 1 . 0 × 10 14 [OH ] = K w [H 3 O + ] = 1 . 0 × 10 14 8 . 2 × 10 5 = 1 . 2 × 10 10 M 005 10.0 points What is [OH ] in a 0.0050 M HCl solution? 1. 6 . 6 × 10 5 M

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amg2845 – hw04 – McCord – (53580) 2 2. 5 . 0 × 10 3 M 3. 2 . 0 × 10 12 M correct 4. 1 . 0 M 5. 1 . 0 × 10 7 M Explanation: [OH ] = 0 . 0050 M Since HCl is a strong acid, it completely dissociates and H + is 0 . 0050 M. HCl H + + Cl K w = [H + ][OH ] = 1 × 10 14 [OH ] = K w [H + ] = 1 × 10 14 0 . 0050 = 2 × 10 12 M 006 10.0 points What is the conjugate acid of NO 3 ? 1. NO 2 2. NO 3 2 3. NH 3 4. H + 5. OH 6. HNO 3 correct Explanation: Since the question asks for the conjugate acid, we can assume NO 3 is acting as a base. This means that it is a proton acceptor. To form the conjugate acid, it accepts a H making HNO 3 .
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hw4 - amg2845 hw04 McCord(53580 This print-out should have...

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