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3 Stoichiometry Solutions to Exercises (c) Analyze. Given: moles. Find: molecules. Plan. Use Avogadro's number. Solve. 1.0x10⁻⁶ mol 6.022 X 10²³ molecules = 6.022x10¹⁷ 1 mol CH₃CH₂OH molecules Check. (6 X = 6 10¹⁷ (d) Analyze. Given: mol Find: N atoms. Plan. mol NH₃ mol N atoms N atoms Solve. 0.410 mol NH₃ X 1 mol N atoms 6.022x10²³ 1 mol atoms 1 mol NH₃ = N atoms Check. 3.34 (a) molar mass = 1(112.41) + 1(32.07) = 144.48 g 1.50x10⁻² mol CdS 144.48 mol = 2.17 CdS 1 (b) molar mass = 1(14.01) + 4(1.008) + 1(35.45) = 53.49 g/mol 86.6 g 53.49g = 1.6190 = 1.62 mol (c) 8.447 X 10⁻² mol C₆H₆ 6.02214 X 10²³ molecules = 5.087 C₆H₆ molecules 1 mol (d) 6.25x10⁻³ mol 1 mol 9molO X 6.022 10²³ 1 mol atoms = 3.39 10²² atoms 3.35 Analyze/Plan. See Solution 3.33 for stepwise problem-solving approach. Solve. (a) (NH₄)₃PO₄ molar mass = 3(14.007) + 12(1.008) + 1(30.974) + 4(16.00) = 149.091 = 149.1 g/mol 1 mol (b) molar mass = 26.982 + 3(35.453) = 133.341 = 133.34 X 133.34 X 1 3 mol mol Cl⁻ = 5.737 mol 1 mol (c) C₈H₁₀N₄O₂ molar mass = 8(12.01) + 10(1.008) + 4(14.01) + 2(16.00) = 194.20 = 1 mol 7.70 molecules molecules 1 mol caffeine 0.406 g cholesterol (d) = 387 g cholesterol/mol 0.00105 mol 46