QUIZ V.1.3 — Mole Calculations and Empirical Formulas1
Mole Calculations and Empirical Formulas
Molecular formula = (Empirical Formula) x n
where: n =
1.Determine the molar mass for the following compounds.
(a)Ag2C2O4______
(b)Fe3(PO4)2______
(c)W3(PO4)7______
(d)Pb(IO3)4 • 6H2O______
2.Calculate the moles in each of the following.
(a)34.7 g of FeCl3______
(b)59.3 g of Ag2SO4______
(c)78.5 L of N2O4(g) at STP______
(d)9.26 L of CO2(g) at STP______
(e)4.45 x 1019 atoms of Sb______
(f)6.48 x 1025 molecules of PCl3______
3.What is the mass of 6.48 L of NH3(g) at STP?
______
4.What is the mass of 1.85 x 1020 molecules of CCl4(l)?
______
5.What volume is occupied by 35.0 g of C3H8(g) at STP?
______
6.What volume is occupied by 8.14 x 1019 molecules of CO2(g) at STP?
______
7.How many molecules of PCl3 are in 100.0 g of PCl3?
______
8.How many “atoms of nitrogen” are there in 16.7 L of N2O4(g) at STP?
______
9.Determine the percentage composition of each of the following. (Express percentages to 1 decimal place)
(a)PbC2O4
______
(b)Na3Fe(CN)6
______
(c)(NH4)2SnCl6
______
(d)Al2(SO4)3 • 3H2O
______
10.Determine the percentage composition of the bold species in each of the following.
(a)Co3(PO4)2 • 8H2O
______
(b)Ce2(C2O4)3 • 9H2O
______
(c)Cu(C2H3O2)2 • 2NH3
______
11.Find the empirical formula for the following compounds.
(a)77.9% I, 22.1% O
(b)24.4% C, 3.39% H, 72.2% Cl
(c)26.6% K, 35.4% Cr, 38.0% O
(d)3.66% H, 37.8% P, 58.5% O
12.A compound has the empirical formula CH3. If the compound has a molecular mass of 120.0 g/mol, what is the molecular formula?
13.The compound methyl butanoate smells like apples. It has a percentage composition of 58.8% C, 9.8% H, and 31.4% O. If its molecular mass is 204 g/mol, what is its molecular formula?
14.A gas has the empirical formula CH2. If 2.73 L of the gas at STP has a mass of 8.52 g, what is the molecular formula?
15.A gas has the empirical formula CH4N. If 0.0762 mol of the compound has a mass of 4.57 g, what is the molecular formula?
16.A compound is 39.7% C, 1.65% H, and 58.7% Cl. If 0.845 L of the gas at STP has a mass of 6.85 g, what is the molecular formula?
17.A compound is composed of 78.3% B and 21.7% H. If 0.0358 mol of the compound has a mass of 0.988 g, what is the molecular formula of the gas?