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Chapter 4 Chemical Quantities and Aqueous Reactions 81 Solution: Balanced Reactions: 2 + + + + 2 + + 1 12 10.0 X 9.300 100.0 2 1 1 7 10.0 X = 1 1 10.0 = 16.584 2 1 Total CO₂ = 9.30 kg + 4.87 kg + 16.6 kg = 30.8 kg CO₂ Check: The units of the answer (kg CO₂) are correct. The magnitude of the answer is reasonable because a large amount of CO₂ is produced per mole of hydrocarbon. Challenge Problems 4.127 Given: g C₃H₈ + C₂H₂ = 2.0 g; mol CO₂ = 1.5 mol H₂O Find: original g C₂H₂ Conceptual Plan: mol mol CO₂ and mol and mol C₂H₂ mol and mol Solution: Let a = mol C₃H₈ and b = mol C₂H₂ C₃H₈ + + + 2CO₂ + H₂O a 4a b 2b b Total mol CO₂ = 3a + 2b and total mol = 4a + b mol CO₂ = 1.5 So + 2b = And a X 1 mol Solve the simultaneous equations: a = 9.98 X 10⁻³ mol C₃H₈ and b = 0.0599 mol C₂H₂. Substitute for b and solve for grams C₂H₂. 0.060 mol C₂H₂ = g = 1.6 g C₂H₂ Check: The units of the answer (g C₂H₂) are correct. The magnitude is reasonable because it is less than the total mass. 4.129 Given: 0.100 L, 1.22 M total mass = 28.1 g Find: g Conceptual Plan: vol, M mol Nal mol I⁻; total mol mol AgI and Solution: 0.100 X 1.22 mol Nal X = 0.122 mol Γ Let = mol AgI and y = x + 2y = 0.122 mol so = 0.061 0.5x Solve the simultaneous equations and x = 0.0504 mol 0.0504 mol X 234.77 1 = 11.8 g Check: The units of the answer (g AgI) are correct. The magnitude is reasonable because it is less than the total mass. 4.131 Given: 3.5 X 10⁻³ M Ca²⁺; 1.1 X 10⁻³ M Mg²⁺; 19.5 gal H₂O; 0.65 kg detergent/load Find: % by mass Na₂CO₃ Conceptual Plan: gal L then V,M mol and V,M mol vol M = mol vol M = mol 1 gal then total moles ions mol mol Na₂CO₃ g kg Na₂CO₃ % Na₂CO₃ 1 mol 1 mol Na₂CO₃ 106.01 g kg Na₂CO₃ X 100% 1 mol ion 1 mol 1 mol Na₂CO₃ 1000 kg detergent Copyright © 2017 Pearson Education, Inc.