Homework 7-solutions - houston(sah4324 Homework 7 fakhreddine(49350 This print-out should have 18 questions b b2 4ac[OH = x = Multiple-choice questions

Homework 7-solutions - houston(sah4324 Homework 7...

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houston (sah4324) – Homework 7 – fakhreddine – (49350) 1 This print-out should have 18 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 1.0points 002 1.0points What would be the pH of a 6 × 10 - 9 M solution of NaOH? 1. 7.016 2. 7.021 3. 7.007 4. 7.013 correct Explanation: For a dilute strong base, [OH - ] 2 - Cb[OH - ] - K w = 0 [OH - ] = x = parenleftBigg - b ± b 2 - 4ac 2a parenrightBigg pOH = 6.987 pH = 7.013 003 1.0points Calculate the resulting pH obtained by mixing 16.5 g HCl and 22.6 g NaCl in water to create 482 L solution. 1. 3.03 correct 2. 5.67 3. 1.13 4. 4.31 5. 2.15 6. 3.92 Explanation: m HCl = 16.5 g m NaCl = 22.6 g V = 482 L The resulting pH is obtained from the [H + ]. ? mol H + = 16 . 5 g HCl × 1 mol HCl 36 . 45 g HCl × 1 mol H + 1 mol HCl × 1 482 L = 9 . 39 × 10 - 4 M H + pH = - log[H + ] = - log[9 . 39 × 10 - 4 ] = 3 . 03 004 1.0points I found some potassium chlorate from inside our lab. I measured some out on a big marble slab. I dissolved it in water, and took a breath of fresh air. The pH No big surprise there. 1. was now basic. 2. remained neutral. correct 3. was acidic. Explanation:
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houston (sah4324) – Homework 7 – fakhreddine – (49350) 2 Potassium chlorate is the salt of a strong acid and strong base and is therefore a NEU- TRAL salt. 005 1.0points Which of the following salts produces a neu- tral solution when it is dissolved in water? 1. KCH 3 CO 2 2. NaClO 3. NaBr correct 4. LiF 5. KCN Explanation: 006 1.0points Identify the list in which all salts produce a basic aqueous solution. 1. KCH 3 COO, NaCN, KF correct 2. AgNO 3 , NaCHO 2 , CrI 3 3. NH 4 Cl, C 6 H 4 NH 3 NO 3 , FeI 3 4. AlCl 3 , Zn(NO 3 ) 2 , KClO 4 5. CH 3 NH 3 Cl, KNO 3 , NaBz (sodium ben- zoate) Explanation: 007 1.0points Which solution has the highest pH? 1. 0.1 M of KClO, K aHClO = 3 . 5 × 10 - 8 correct 2. 0.1 M of KCH 3 COO, K aHC 2 H 3 O 2 = 1 . 8 × 10 - 5 3. 0.1 M of KNO 2 , K aHNO 2 = 4 . 5 × 10 - 4 4. 0.1 M of KCl, K aHCl = very large 5. 0.1 M of KHCOO, K aHCOOH = 1 . 8 × 10 - 4 Explanation: 008 1.0points
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