c formula units of potassium iodide a moles of beryllium b moles of calcium c mole of sulfur a. 6.

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1 Chapter Identify and calculate the number of representative particles in each of the following quantities. a moles of gold 2.15 mol Au atoms Au b mole of nitrogen oxide 0.15O c moles of potassium bromide 11.5 mol KBr atoms Au 1 mol Au molecules NO molecules NO O formula units KBr 1 mol KBr formula units KBr c formula units of potassium iodide formula units KI 1 mol KI formula units KI mol KI 3. Determine the mass in grams of each of the following quantities. a moles of beryllium 1.24 mol Be 11.2 g Be b moles of calcium 3.35 mol Ca 134 g Ca 9.01 g Be 1 mol Be g Ca a 2. Calculate the number of moles of the substance that contains the following number of representative particles. a atoms of barium atoms Ba 1.48 mol Ba b molecules of carbon monoxide molecules CO O molecules CO 91.4 mol CO 1 mol Ba atoms Ba c mole of sulfur mol S 4.97 g S 4. Calculate the number of moles in each of the following quantities. a g lithium 6.35 g Li mol Li b. 346 g zinc 346 g Zn 5.29 mol Zn g S 1 mol Li 6.94 g Li 1 mol Zn g Zn 58 Chemistry: Matter and Change Supplemental Problems Answer Key

2 c. 115 g nickel 115 g Ni 1.96 mol Ni i g Ni b atoms of cadmium d atoms Cd atoms Cd g Cd d g Cd 5. How many atoms are in the following samples? a g cobalt o 1.24 g Co g Co atoms Co o atoms Co c atoms of argon 1 mol Ar atoms Ar atoms Ar g Ar 1 mol Ar 88.3 g Ar The quantity atoms of radium has the greatest mass. b g cesium e g Ce g Ce atoms Ce e atoms Ce 7. Calculate the number of moles in each of the following quantities. a. atoms of each element in 3.35 moles of aspirin (C 9 H 8 O 4 c g silicon i 65.6 g Si g Si atoms Si i atoms Si 6. Which quantity has the greatest mass? a atoms of radium 1 mol Ra atoms Ra atoms Ra 226 g Ra 1 mol Ra 156 g Ra 9 mol C 3.35 mol C 9 H 8 O mol C 9 H 8 O 4 8 mol H 3.35 mol C 9 H 8 O mol H 9 H 8 O 4 4 mol O 3.35 mol C 9 H 8 O mol O 9 H 8 O 4 b. positive and negative ions in 1.75 moles of calcium fluoride (CaF 2 a 1.75 mol CaF mol Ca af mol F 1.75 mol CaF mol F af 2 Supplemental Problems Answer Key Chemistry: Matter and Change 59

3 8. Determine the molar mass of each of the following compounds. a. formic acid (CH 2 O 2 H 2 O 2 H 2 O g C 2 mol H H 2 O 2 H 2 O g H 2 mol O H 2 O 2 H 2 O g O g C (12.01 g 2.02 g g g The molar mass of formic acid is g/mol. b. ammonium dichromate ((NH 4 2 Cr 2 O 7 9. What is the mass in grams of each of the following quantities? a moles of lead(ii nitrate (Pb(NO mol Pb 1 mol Pb(NO mol Pb(NO g Pb g Pb 1 mol Pb 2 mol N 1 mol Pb(NO mol Pb(NO g N 6 mol O 1 mol Pb(NO mol Pb(NO g O (207.2 g g g g The molar mass of lead(ii nitrate is g/mol. 2 mol N 1 mol (NH 4 2 Cr 2 O 7 1 mol (NH 4 2 Cr 2 O g N 8 mol H 1 mol (NH 4 2 Cr 2 O 7 1 mol (NH 4 2 Cr 2 O g H 2 mol Cr 1 mol (NH 4 2 Cr 2 O 7 1 mol (NH 4 2 Cr 2 O g Cr g Cr 7 mol O 1 mol (NH 4 2 Cr 2 O 7 1 mol (NH 4 2 Cr 2 O g O (28.02 g 8.08 g g g g The molar mass of ammonium dichromate is g/mol mol Pb(NO g b moles of magnesium bromide (MgBr 2 1 mol Mg 1 mol MgBr 2 1 mol MgBr g Mg g Mg 1 mol Mg 2 mol Br 1 mol MgBr 2 1 mol MgBr g Br g Br 1 mol Br (24.31 g g g The molar mass of magnesium bromide is g/mol mol MgBr g g Pb(NO mol Pb(NO 3 2 The mass of 2.53 moles of lead(ii nitrate is 838 g g MgBr 2 1 mol MgBr 2 The mass of 4.62 moles of magnesium bromide is 851 g. 60 Chemistry: Matter and Change Supplemental Problems Answer Key

4 10. Calculate the number of moles in each of the following samples. a g calcium carbide (CaC 2 2 mol C ac 2 ac g C a ac 2 ac g Ca g C b. 245 g aluminum nitrite (Al(NO 2 3 (24.02 g g g The molar mass of calcium carbide is g/mol g CaC mol CaC 2 ac g CaC g Ca a 11. Determine the percent composition of each of the following compounds. a. manganese oxide (MnO O g Mn O O (54.94 g g g g Mn The molar mass of manganese oxide is g/mol g Mn mass percent Mn g MnO 77.45% Mn mass percent O g MnO 22.55% O O g Al (NO 2 3 (NO g Al 3 mol N (NO 2 3 (NO g N 6 mol O (NO 2 3 (NO g O (26.98 g g g g The molar mass of aluminum nitrite is g/mol. 245 g Al(NO mol Al(NO 2 3 (NO g Al(NO 2 3 b. propanol (C 3 H 8 O 3 mol C 3 H 8 O 3 H 8 O g C 8 mol H 3 H 8 O 3 H 8 O 8.08 g H 3 H 8 O 3 H 8 O g C (36.03 g 8.08 g g g The molar mass of propanol is g/mol g C mass percent C g C 3 H 8 O 59.94% C 8.08 g H mass percent H g C 3 H 8 O 13.44% H mass percent O g C 3 H 8 O 26.62% O Supplemental Problems Answer Key Chemistry: Matter and Change 61

5 c. calcium phosphate (Ca 3 (PO mol Ca a 3 (PO 4 2 a 3 (PO g Ca a 12. Determine the empirical formula for a g sample of a compound having the following percent composition. a % sulfur and 5.93% hydrogen In a g sample: mass of S g mass of H 5.93 g g S 2.93 mol S g S 5.93 g H 5.87 mol H 5.87 mol H 2.93 mol S 2.00 mol H 1.00 mol S 2 mol H 2.93 mol S 2.93 mol S 1.00 mol S 1.00 mol S 2 mol H : g Ca 2 mol P a 3 (PO 4 2 a 3 (PO g P 1 mol P g P 8 mol O a 3 (PO 4 2 a 3 (PO g O ( g g g g The molar mass of calcium phosphate is g/mol g Ca mass percent Ca g Ca 3 (PO % Ca g P mass percent P g Ca 3 (PO % P g O mass percent O g Ca 3 (PO % O The empirical formula is H 2 S. b % mercury, 12.87% oxygen, and 6.45% sulfur Mass of Hg g Hg Mass of O g O Mass of S 6.45 g S g g Hg mol Hg g Hg g O mol O 6.45 g S g S mol Hg mol O A g sample of an aluminum-iodine compound contains 3.20 g of aluminum. What is the empirical formula for the compound? g compound 3.20 g Al g I 3.20 g Al mol Al g Al 1 mol I g I mol I g I mol I mol Al mol Al mol Al 3 mol I : mol I mol Al mol Al mol Al The empirical formula is AlI mol Hg mol O 2 mol Hg : 4 mol O : The empirical formula is Hg 2 SO 4. 3 mol I 2 mol Hg 4 mol O 62 Chemistry: Matter and Change Supplemental Problems Answer Key

6 14. A g sample of hydrated manganese(ii chloride yields g of the anhydrous compound after heating. Determine the chemical formula and name the hydrate g hydrate g anhydrous compound g water Cl 2 Cl g Mn Cl g Cl 2 mol Cl Cl 2 (54.94 g g g The molar mass of manganese(ii chloride is g/mol g MnCl 2 Cl g MnCl g Mn g Cl l g C mol C g C g N mol N g O 5.20 g H 5.15 mol H mol C mol N 5.15 mol H mol C mol N 5.00 mol H 1.00 mol O 4 mol C 2 mol N 5 mol H 4 mol C : 2 mol N : 5 mol H : The empirical formula of caffeine is C 4 H 5 N 2 O mol MnCl g H 2 O mol H 2 O mol H 2 O mol H 2 O mol MnCl mol MnCl 2 4 mol H 2 O Cl 2 2 O g H 2 O The ratio of water to manganese dichloride is 4 : 1. The chemical formula of the hydrate is MnCl 24H 2 O and its name is manganese(ii chloride tetrahydrate. 15. Caffeine is a compound found in some natural coffees and teas and in some colas. a. Determine the empirical formula for caffeine, using the following composition of a g sample grams of carbon, grams of nitrogen, grams of oxygen, and 5.20 grams of hydrogen b. If the molar mass of caffeine is g/mol, calculate its molecular formula g C 4 mol C g C 2 mol N g N 5 mol H 5.05 g H (48.04 g g 5.05 g g g The molar mass of the empirical formula is g/mol. molar mass of compound n molar mass of empirical formula g/mol g/mol The molecular formula for caffeine is (C 4 H 5 N 2 O2, which is C 8 H 10 N 4 O 2 Supplemental Problems Answer Key Chemistry: Matter and Change 63