Quiz2 - Version 014/AAADC Quiz 2 Lyon(53385 This print-out...

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Version 014/AAADC – Quiz 2 – Lyon – (53385) 1 This print-out should have 3 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 1 2 3 4 5 BACK NEXT AA AB AC AD BA CC CD 001 10.0 points A mixture of NaNO 3 and Na 2 SO 4 of mass 5.37 g contains 1.61 g of sodium. What is the percentage by mass of NaNO 3 in the mixture? 1. 40.2% NaNO 3 2. 30.6% NaNO 3 3. 45.3% NaNO 3 correct 4. 60.7% NaNO 3 5. 35.4% NaNO 3 6. 50.3% NaNO 3 Explanation: m total = 5.37 g m Na = 1.61 g Let x = g of mol NaNO 3 Then 5 . 37 - x = g of Na 2 SO 4 Find the weight % of Na in each compound Na NaNO 3 = 23 . 0 23 . 0 + 14 . 0 + 3(16 . 0) × 100% = 27 . 1% Na Na 2 SO 4 = 2(23 . 0) 2(23 . 0) + 32 . 07 + 4(16 . 0) × 100% = 32 . 4% Therefore (%Na NaNO 3 )(m NaNO 3 ) +(%Na Na 2 SO 4 )(m Na 2 SO 4 ) = 1 . 61 g parenleftbigg 27 . 1 100 parenrightbigg x + parenleftbigg 32 . 4 100 parenrightbigg (5 . 37 - x ) = 1 . 61 1 . 739 - 1 . 61 = 0 . 324 x - 0 . 271 x 0 . 053 x = 0 . 129 x = 2 . 434 g Thus %NaNO 3 = 2 . 434 g 5 . 37 g × 100% = 45 . 3% 002 10.0 points Which of the following is a chemical change?
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