Chapter 7

- Chapter 7 -61. Percent composition of C 17 H 21 NOHCl 17 C 204.2 g 204:2gC22 H 22.18 gð100Þ ¼ 69:98% C291:8gN 14.01 g 22:18 g HO16.00 gð100Þ ¼ 7:60% H291:8gCl 35.45 g 14:01 g N291.8 gð100Þ ¼ 4:80% N291:8g16:00 g Oð100Þ ¼ 5:48% O291:8g35:45 g Clð100Þ ¼ 12:15% Cl291:8g62. Percent composition of sucrose 12 C 144.1 g 144:1gC22 H 22.18 gð100Þ ¼ 42:10% C342:3g11 O 176.0 g 22:18 g H342.3 gð100Þ ¼ 6:480% H342:3g176:0gOð100Þ ¼ 51:42% O342:3g63. Molecular formula of aspirin60.0% C, 4.48% H, 35.5% O; molar mass of aspirin ¼ 180.2 1 mol C5:00 mol Cð60:0gCÞ¼ 5:00 mol C¼ 2:25 mol C12:01 g C2:22 1 mol H4:44 mol Hð4:48 g HÞ¼ 4:44 mol H¼ 2:00 mol H1:008 g H2:22 1 mol O2:22 mol Oð35:5gOÞ¼ 2:22 mol O¼ 1:00 mol O16:00 g O2:22Multiplying each by 4 give the empirical formula C 9 H 8 O 4 . The empirical formula mass is 180.2 g. Sincethe empirical formula mass equals the molar mass, the molecular formula is the same as the empiricalformula, C 9 H 8 O 4 .64. Calculate the percent oxygen in Al 2 (SO 4 ) 3 . 2Al 53.96 g 192:0g3S96.21 gð100Þ ¼ 56:11% O342:2g12 O 192.0 g Now take 56:11% of8:50 g342.2 g 8:50 g Al 2 ðSO 4 Þ 3 ð0:5611Þ¼ 4:77 g O-70-