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Percent Composition and Empirical formula Practice.

(from Hebden)

44. Calculate the percentage composition of the all the elements in the following compounds: a) C2H6 h) (NH4)3PO4 b) FeCl2 i) Ag(NH3)2Cl j) C17H15N3O2Cl c) FeCl3 k) Sn(SO4)2·2H2O d) C2H4O2 l) (NH4)Sn(OH)6 e) CaCO3 m) C2H4N2O4 f) NaOH g) CaCl2·2H2O n) K3Fe(CN)6

45. Calculate the percentage of the bold species in each of the following compounds: a) CaCl2·2H2O e) Cr(NH3)6Cl3·H2O b) NiSO4·7H2O f) Cr(NH3)6Cl3·H2O c) Ce2(C2O4)3·9H2O g) Cu(C2H3O2)2·2NH3 d) Al2(SO4)3·18H2O h) Fe2(SO4)3·9H2O 46. Find the empirical formula for the following compounds. a) 15.9% B, 84.1% F h) 46.3% b) 87.5% Si, 12.5% H i) 24.4% c) 43.7% P, 56.3% O j) 26.6% d) 77.9% I, 22.1% O k) 21.8% e) 77.7% Fe, 22.3% O l) 3.66% f) 70.0% Fe, 30.0% O m) 46.2% g) 72.4% Fe, 27.6% O n) 50.5%

Li, 53.7% O C, 3.39% H, 72.2% Cl K, 35.4% Cr, 38.0% O Mg, 27.9% P, 50.3% O H, 37.8% P, 58.4% O C, 7.69% H, 46.2% O C, 5.26% H, 44.2% N

47. A gas has the empirical formula CH2. If 0.850 L of the gas at "STP" has a mass of 1.59 g, what is the molecular formula of the compound? 48. A gas has the percentage composition: 30.4% N and 69.6% O. If the density of the gas is 4.11 g/L at "STP", what is the molecular formula of the gas? 49. A compound has an empirical formula C 5H11. If 0.0275 mol of the compound has a mass of 3.91 g, what is the molecular formula of the compound? 50. A gas has an empirical formula CH. If 450 mL of the gas at "STP" has a mass of 0.522 g, what is the molecular formula of the compound? 51. When a sample of nickel carbonyl is heated, 0.0600 mol of a gas containing carbon and oxygen is formed. The gas has a mass of 1.68 g and is 42.9 % C. What is the molecular formula of the gas? 52. When a sample of analyzed and found to contain 33.0% Si and 67.0% F. If the gas density is 7.60 g/L at "STP", what is the molecular formula of the gas? 53. A gas has a percentage composition: 78.3% B and 21.7% H. A sample of the unknown gas is found to have a mass that is 0.986 times the mass of the same volume of N 2 gas, at the same temperature and pressure. What is the molecular formula of the unknown gas? Hint: both gasses have the same number of mol; find 0.986 of the molar mass of N2 and use it with the empirical formula of the unknown gas....