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Exam1AKey

# Exam1AKey - 1 Consider the compound benzotrichloride...

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1) Consider the compound benzotrichloride, C 7 H 5 Cl 3 . a) (12) What is the molar mass of the compound? C : 7 x 12.01 = 84.07 g C 7 mol C 7 x N A C atoms H : 5 x 1.008 = 5.040 g H 5 mol H 5 x N A H atoms Cl : 3 x 35.45 = 106.35 g Cl 3 mol Cl 3 x N A Cl atoms 195.46 g cpd 1 mol cpd N A C 7 H 5 Cl 3 molecules molar mass = 195.46 g/mol b) (12) How many grams of carbon are in a sample that contains 0.850 moles of H? 0.850 mol H x H mol 5 C g 84.07 = 14.3 g C mass = 14.3 g c) (12) What mass of compound contains 2.20 x 10 24 chlorine atoms? 2.20 x 10 24 Cl atoms x atoms Cl 10 x 6.02 x 3 cpd g 46 . 195 23 = 238 g cpd mass = 238 g 2) Coumaran was found to be 79.97% C, 6.71% H, and 13.32% O by mass. The molar mass was determined to be 120 g/mol. a) (20) What is the simplest (empirical) formula of coumaran? C : 79.97 g x g 12.01 mol 1 = 6.659 mol / 0.8325 = 8 H : 6.71 g x g 1.008 mol 1 = 6.657 mol / 0.8325 = 8 O : 13.32 g x g 16.00 mol 1 = 0.8325 mol / 0.8325 = 1 simplest formula : C 8 H 8 O b) (12) What is the molecular formula of coumaran? M m = 8(12.01) + 8(1.008) + 1(16.00) = 120 molecular formula : C 8 H 8 O

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3) (18) How many mL of a 1.20 M stock solution of KCl are required to prepare 400.0 mL of 0.250 M solution?
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