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fak chem hw 5 - To(st22362 Homework 5 Fakhreddine(52420...

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To (st22362) – Homework 5 – Fakhreddine – (52420) 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 1.0 points A solution of NaOH(aq) contains 5 . 9 grams of NaOH in 276 mL of solution. Calculate the pH at 25 C. Correct answer: 13 . 728. Explanation: m NaOH = 5 . 9 g V = 276 mL NaOH is a strong acid which completely dissociates in water. NaOH(aq) -→ Na + + OH [OH ] = [NaOH ] = parenleftbigg 5 . 9 g NaOH 0 . 276 L soln parenrightbigg parenleftbigg 1 mol NaOH 39 . 99 g NaOH parenrightbigg = 0 . 534554 pH = 14 - pOH = 14 + log[OH ] = 13 . 728 002 1.0 points The pH of a solution of Ba(OH) 2 is 9.40. What is the molarity of the Ba(OH) 2 solu- tion? 1. 1 . 8 × 10 5 M 2. 5 . 0 × 10 5 M 3. 8 . 3 × 10 4 M 4. 1 . 3 × 10 5 M correct 5. 2 . 5 × 10 5 M Explanation: 003 1.0 points Like all equilibrium constants, K w varies somewhat with temperature. Given that K w is 4 . 95 × 10 13 at some temperature, what is the pH of a neutral aqueous solution at that temperature? 1. 6.22 2. 6.34 3. 6.06 4. 6.43 5. 6.15 correct Explanation: 004 1.0 points A 0.200 M solution of a weak monoprotic acid HA is found to have a pH of 3.00 at room temperature. What is the ionization constant of this acid? 1. 1.0 × 10 3 2. 5.30 3. 5.0 × 10 3 4. 2.0 × 10 9 5. 2.0 × 10 5 6. 1.0 × 10 6 7. 1.8 × 10 5 8. 5.0 × 10 6 correct Explanation: 005 1.0 points Which of the following solutions has the low- est pH at 25 C? 1. 0.5 M formic acid correct 2. 0.5 M aniline 3. 0.1 M ammonia 4. 0.1 M acetic acid
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To (st22362) – Homework 5 – Fakhreddine – (52420) 2 Explanation: 006 1.0 points A 0.00100 M solution of a weak acid HX is 8% ionized. Calculate K a for the acid. Correct answer: 6 . 95652 × 10 6 . Explanation: 007 1.0 points A 7 . 2 × 10 3 M solution of acetic acid is 5.0% dissociated. In a 7 . 2 × 10 4 M solution, the percent dissociation would be 1. zero. 2. > 5%. correct 3. None of these 4. < 5%. 5. the same. Explanation: 008 1.0 points An aqueous solution of nitrous acid HNO 2 has a pH of 1.96. The ionization constant of this acid is 5.0 × 10 4 . How much nitrous acid was used to prepare one liter of this solution? (Approximate the full quadratic equation.) Correct answer: 11 . 3 grams.
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