University:
Central Michigan University
Course:
CHM 351 | Physical Chemistry I
Academic year:

2020
Views:

125

Pages:

3
Author:

almerazne

Empirical Formula Problems – Set I 1. Determine the empirical formula of a compound consisting of : (a) 55.3%K, 14.6%P, and 30.1% O. (K3PO4) (c) 52.14%C, 13.13%H, and 34.73% O. (C2H6O) (b) 47.3% Cu and 52.7% Cl. (CuCl2) (d) 40.0%C, 6.73%H and 53.3% O . 2. In vanadium oxide, the mole ratio is calculated to be: 2.50 mol O/1 mol V. What is the simplest formula of vanadium oxide ? (V2O5) 3. Some phosphorus is heated in air to produced phosphorus oxide. The following data was collected: mass of crucible (reaction vessel) mass of crucible + phosphorus mass of crucible + phosphorus oxide 25.34 g 27.19 g 29.58 g (a) Determine the empirical formula of phosphorus oxide. (P2O5) (CH2O) 4. Phosphorus forms two different compounds with chlorine. One compound contains 22.5 % P by mass, and the other contains 14.87 % P by mass. Determine the empirical formulas of the two compounds. (PCl3 ; PCl5) 5. An ace chemistry student carries out the following reaction in an attempt to determine the empirical formula of a copper oxide: CuxOy(s) + CH4(g) + heat  Cu(s) + H2O(g) + CO2(g) Mass of empty test tube Mass of empty test tube + copper oxide Mass of copper oxide Mass of test tube + solid copper(after heating) Mass of copper (in copper oxide) Mass of oxygen (in copper oxide) 24.25 g 26.26g 25.85 g Complete the above data table and determine the empirical formula of copper oxide. 6. An ace chemistry student heats a piece of iron(Fe) metal in a crucible. The reaction is: Fe(s) + O2(g)  FexOy(s) . Complete the data below. Determine the empirical formula of iron oxide. Show all your work. mass of crucible mass of crucible + Fe mass of Fe mass of crucible + iron oxide mass of iron oxide moles of Fe mass of oxygen moles of oxygen 27.50 g 28.62 g 29.10 g Empirical + Molecular Formula Problems – Set II 1. What is the empirical formula of the following compounds: (a) C4O12 __________ (b) SiO2 _________ (c) N4H8Cl2 __________ 2. A 10.00 g sample of vitamin C was analyzed and found to contain 4.092 g of C, 0.458 g of H, and 5.450 g of O. Given that the molar mass of the compound is 176g, determine the molecular formula of vitamin C. (answer: C6H8O6) 3. Cyclobutane has the empirical formula CH2. Its molar molar mass is 42g. What is its molecular formula? (answer: C3H6) 4. The amino acid Histidine has a molar mass of 154g. Is the molecular formula of Histidine C3H4NO or C6H8N3O2? 5. The major air pollutant of coal-burning power plants is a colorless, pungent gaseous compound containing only sulfur and oxygen. Chemical analysis of a 1.078 g sample of this gas showed that it contained 0.540 g of S and 0.538 g of O. What is the empirical formula of this compound? (answer: SO2). 6. Determine the empirical formula of a compound containing: 29.2% N, 8.3% H, 12.5% C, and 50.0 % O. (answer: N2H8CO3) 7. Benzene has the empirical formula CH. Its molar mass is 78g. What is its molecular formula? (answer: C6H6)

Empirical and Molecular Formula Answers

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