Back Lesson Print Name Class Date Skills Worksheet Concept Review Section: Formulas and Percentage Composition Solve the following problems, and write your answer in the space provided. 1. The mineral greenockite is a yellow sulfide of cadmium that is 78.0% cadmium and 22.0% sulfur. Determine the empirical formula of greenockite. 2. What is the empirical formula for a compound of aluminum and fluorine that is 32% aluminum and 68% fluorine? 3. What is the empirical formula for a compound that is 26.56% potassium, 35.41% chromium, and 38.03% oxygen? 4. What is the empirical formula for a compound that is 33.36% calcium, 26.69% sulfur, and 40.00% oxygen? Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Chemistry 5 The Mole and Chemical Composition Back Lesson Print Name Class Date Concept Review continued 5. What is the empirical formula for a compound that is 29.44% calcium, 23.55% sulfur, and 47.01% oxygen? This compound is a common ingredient in plaster. 6. The empirical formula of a compound is CH. The experimental molar mass is 78.12 g/mol. Determine the molecular formula of the compound. 7. The empirical formula of a compound is CH2O. The experimental molar mass is 60.06 g/mol. Determine the molecular formula of the compound. 8. The empirical formula of a substance is P2O5. The experimental molar mass is 283.89 g/mol. Determine the molecular formula of the compound. Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Chemistry 6 The Mole and Chemical Composition Back Lesson Print Name Class Date Concept Review continued 9. The empirical formula of a substance is BH3. The experimental molar mass is 27.67 g/mol. Determine the molecular formula of the compound. 10. The empirical formula of a compound is CH. The experimental molar mass is 26.04 g/mol. Determine the molecular formula of the compound. 11. Quartz has the chemical formula SiO2. What is the percentage composition of this compound? 12. Urea, a component in fertilizer, has the chemical formula, CO(NH2)2. What is the percentage composition of this compound? Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Chemistry 7 The Mole and Chemical Composition Back Lesson Print Name Class Date Concept Review continued 13. Fructose, a sweetener in soft drinks, has the chemical formula C6H12O6. What is the percentage composition of this compound? 14. Which of two common ingredients in garden fertilizers, ammonium sulfate, (NH4)2SO4, or ammonium phosphate, (NH4)3PO4, has a greater percentage of nitrogen? 15. Which compound has the greater percentage of zinc—smithsonite, ZnCO3, or sphalerite, ZnS? Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Chemistry 8 The Mole and Chemical Composition Back Lesson Print TEACHER RESOURCE PAGE Answer Key Concept Review: Avogadro’s Number and Molar Conversions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. FOUR STEPS FOR SOLVING QUANTITATIVE PROBLEMS 1. 2. 3. 4. 5. 6. 2.41 1024 atoms Al 9.33 1023 atoms Na 44.0 mol F 70.7 mol H2 291 mol K 877 g Sb 119 g U 167 g Fr 0.7239 mol Pb 2.54 x 105 mol Au Concept Review: Relative Atomic Mass and Chemical Formulas 1. 2. 3. 4. 5. 6. 7. 8. Additional Problems 85.47 amu 35.45 amu 310.18 g/mol 79.88 g/mol 84.01 g/mol 94.12 g/mol 26.04 g/mol 18.02 g/mol 7. 8. 9. 10. 11. 12. 13. 14. 15. 0.026 mm 3.21 L 0.80 g/cm3 21.4 g/cm3 30 boxes a. 1.73 L 0.120 m 0.120 m 0.120 m b. 9.2 g; 5.0 cm3 c. 60.4 kg; 1.88 104 dm3 d. 0.94 g/cm3; 5.3 104 m3 e. 2.5 103 kg; 2.7 106 cm3 2.8 g/cm3 a. 0.72 m b. 2.5 103 atoms 1300 L/min 1.3 106 cal/h 5.44 g/ cm3 2.24 104 cm3 32 000 uses 2500 L 9.5 L/min MOLE CONCEPT 1. a. b. c. d. e. f. 2. a. b. c. d. e. f. 3. a. b. c. d. e. f. Concept Review: Formulas and Percentage Composition 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. CdS AlF3 K2Cr2O7 CaSO3 CaSO4 C6H6 C2H4O2 P4O10 B2H6 C2H2 Si 46.75%, O 53.25% 19.99% C, 26.64% O, 46.65% N, 6.73% H 39.99% C, 6.73% H, 53.28% (NH4)3PO4 has the greater percentage of nitrogen. 15. Sphalerite, ZnS, has the greater percentage of zinc. 3.7 104 mol Pd 150 mol Fe 0.040 mol Ta 5.38 105 mol Sb 41.1 mol Ba 3.51 108 mol Mo 52.10 g Cr 1.5 104 g or 15 kg Al 8.23 107 g Ne 3 102 g or 0.3 kg Ti 1.1 g Xe 2.28 105 g or 228 kg Li 1.02 1025 atoms Ge 3.700 1023 atoms Cu 1.82 1024 atoms Sn 1.2 1030 atoms C 1.1 1021 atoms Zr 1.943 1014 atoms K Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Chemistry 109 The Mole and Chemical Composition