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# solutions - Version 012 Exam 3 McCord(91750 This print-out...

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Version 012 – Exam 3 – McCord – (91750) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points How many moles oF HCl gas are produced iF 5.00 L oF Cl 2 and excess H 2 are reacted at STP? H 2 + Cl 2 2 HCl(g) 1. 224 mol 2. 0.446 mol correct 3. 0.0112 mol 4. 0.223 mol 5. 8.96 mol 6. 112 mol Explanation: V Cl 2 = 5.00 L At STP we can use the standard molar volume, 22 . 4 L mol , to convert L oF Cl 2 to moles oF Cl 2 : 5 . 00 L × mol 22 . 4 L = 0 . 223 mol Cl 2 Now calculate moles oF H 2 : ? mol H 2 = 0 . 223 mol Cl 2 × 2 mol HCl 1 mol Cl 2 = 0 . 446 mol 002 10.0 points In an improved version oF the gas law, P is replaced by p P + n 2 a V 2 P . Which oF the Following would you predict has the largest a ? 1. Ar 2. H 2 O correct 3. H 2 4. CH 4 5. O 2 6. N 2 7. He 8. Ne Explanation: The strongest attractive Forces occur in wa- ter which exhibits hydrogen bonding. NH 3 also has hydrogen bonding, but not as strong as in water (remember that water has higher melting and boiling points than ammonia). The other choices only exhibit London forces . 003 10.0 points Which oF the Following compounds would have the highest melting point? 1. Al 2 O 3 correct 2. NaCl 3. CaCl 2 4. Na± 5. CaO Explanation: 004 10.0 points A sample oF gas at 200 C has a volume oF 5 L. The volume expands to 10 L due to a temperature change at constant pressure. What will be the new temperature? 1. 400 C 2. 100 C 3. 673 C correct 4. 0 C

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Version 012 – Exam 3 – McCord – (91750) 2 5. - 36 . 5 C Explanation: V 1 = 5 L V 2 = 10 L T 1 = 200 C + 273 = 473 K Applying Charles’ Law, V 1 T 1 = V 2 T 2 T 2 = V 2 T 1 V 1 = (10 L) (473 K) 5 L = 946 K - 273 = 673 C 005 10.0 points If the average speed of a carbon dioxide molecule is 410 m · s 1 at 25 C, what is the average speed of a molecule of methane at the same temperature? 1. 1130 m · s 1 2. 410 m · s 1 3. 680 m · s 1 correct 4. 1000 m · s 1 5. 247 m · s 1 Explanation: 006 10.0 points What is the molecular weight of a (hypothet- ical) gas that diFuses 1.414 times faster than nitrogen (N 2 )? 1. 32.6 g/mol 2. 4.85 g/mol 3. 23.5 g/mol 4. 46.6 g/mol 5. 14.0 g/mol correct Explanation: 007 10.0 points If no change in composition occurs, what will happen to viscosity as temperature decreases? 1.
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solutions - Version 012 Exam 3 McCord(91750 This print-out...

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