Empirical Formula Beginning of Mole

Name __________________________________ Hour______ Empirical Formula Problems – Set I 1. Determine the empirical formula of a compound consisting of : 55.3%K, 14.6%P, and 30.1% O. 47.3% Cu and 52.7% Cl. (K3PO4) (CuCl2) 52.14%C, 13.13%H, and 34.73% O. (C2H6O) 40.0%C, 6.73%H and 53.3% O. (CH2O) 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) 25.34 g mass of crucible + phosphorus 27.19 g mass of crucible + phosphorus oxide 29.58 g Determine the empirical formula of phosphorus oxide. (P2O5) 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 24.25 g Mass of empty test tube + copper oxide 26.26g Mass of copper oxide Mass of test tube + solid copper(after heating) Complete the data table and determine the empirical formula of copper oxide. (CuO) 25.85 g Mass of copper (in copper oxide) Mass of oxygen (in 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. (Fe2O3) mass of crucible 27.50 g mass of crucible + Fe 28.62 g mass of Fe mass of crucible + iron oxide mass of iron oxide moles of Fe mass of oxygen moles of oxygen 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) Moles problem set I 1. Determine the molar mass of each of the following compounds a. HClO3 c. Ca(NO3)2 b. (NH4)2S d. UF6 2. Calculate the number of grams in 0.03 mol of each of the compounds listed in question one. a. c. b. d. 3. Calculate the number of moles contained in 100.0 g of each compound listed in question one. c. a. b. d. 4. In 3.01x1024 molecules of water: a. How many moles of water are present? b. How many grams of water are present? 5. How many atoms are in 2.4 mol of Copper? 6. Calculate the molar mass of: a. NaHCO3 b. Mg(NO3)2 c. (NH4)3PO4 7. Calculate the mass of a. 0.948 mol NaHCO3 b. 3.67 mol Mg(NO3)2 c. 0.294 mol (NH4)3PO4 8. Calculate the number of moles in a. 9.67 g of NaHCO3 b. 38.4 g of Mg(NO3)2 c. 0.754 g of (NH4)3PO4 9. Calculate the percent composition of a. NaHCO3 b. Mg(NO3)2 c. (NH4)3PO4 10. Calculate the number of grams of oxygen in 25.0g of a. NaHCO3 b. Mg(NO3)2 c. (NH4)3PO4 MOLES PROBLEM SET II 1. Determine the molar mass of the following compounds a. Fe3(PO4)2 b. Hemoglobin (C2952H4664O832S8Fe4) 2. Tin (II) fluoride is added to toothpaste to prevent tooth decay. In 24 g of SnF2, how many moles are present? 3. How many mol of benzene (C6H6) are present in 15.6 g benzene? 4. How many grams of NH4Cl are present in 0.4 mol of ammonium chloride? 5. Define molar mass 6. Calculate the molar mass of a compound if 0.22 mol of it weights 48 g. 7. Which sample contains the largest number of hydrogen atoms? a. 7.2 g H2O b. 0.4 mol H2O c. 0.8 g H2 d. 6.02 x 1023 molec H2 8. Which of the following has more atoms? 2.4 g of He or 10.4 g of Cr? Show your work. 9. Determine the molar mass of each of the following compounds a. H2SO4 b. Cu(NO3)2 10. Calculate the number of grams contained in 0.42 mol of each of the compounds in question 9 a. b. 11. How many sugar molecules (C6H12O6) are there in a sugar cube weighing 3.6 g? 12. Calculate the number of moles contained in 200.0 g of each compound listed in question ONE of mole problems set II 13. Calculate the percent composition of H2SO4 14. In 80 g of H2SO4 how many grams of S are present? PERCENT COMPOSITION PRACTICE PROBLEMS 1. A 43.40 mg sample of alcohol contains 15.10 mg O, 22.6 mg C, and the rest is hydrogen. What is the percent composition? 2. Ethyl mercaptan is an odorous substance added to natural gas to make leaks easily detectable. A sample of ethyl mercaptan was composed of 1.64 g S, 1.23 g C, and 0.30 g hydrogen. What is the percent composition? 3. Calculate the percent composition of each of the following compounds a. CO c. KMnO4 b. CO2 d. Co(NO3)2 4. Cadaverine, one of the compounds responsible for the odor of decaying flesh, has the formula NH2CH2CH2CH2CH2 CH2NH2. What is the percent composition of cadaverine? 5. Which contains more carbon? 4.71 g of glucose (C6H12O6) or 5.85 g of ethanol (C2H6O)? 6. A sample of an alloy of aluminum contains 0.0972 mol of Al and 0.0381 mol Mg. a. What is the percent composition? b. How many grams of the alloy are needed to supply 150.0g of Al?