University:
Campbell University
Course:
CHEM 111 | General Chemistry I
Academic year:

2023
Views:

454

Pages:

1
Author:

Scalondrof10

Quiz - Percent Composition, Empirical and Molecular Formula Name: 1.) Calculate the Percentage composition of the following compounds. (4) a.) (NH₄)₃PO₄ (3 × 14.01) + (12 × 1.01) + 30.97 + (4 × 16.00) = 149.12 (molar mass) % N = (3 × 14.01 / 149.12) × 100 = 28.13% % H = (12.12 / 149.12) × 100 = 8.13% % P = 30.97 / 149.12 = 20.77% % O = 64.00 / 149.12 = 42.92% b.) The % H₂O in CaCl₂•2H₂O 40.08 + (2 × 35.45) + (4 × 1.01) + (2 × 16.00) = 147.02 (molar mass) % H₂O = (36.04 / 147.02) × 100 = 24.51% 2.) What is the empirical formula for the following compounds? (5) a.) 72.4% Fe and 27.6% O (2) 72.4 g Fe × 1 mol Fe / 55.85 g Fe = 1.30 mol Fe atoms 27.6 g O × 1 mol O / 16.00 g O = 1.73 mol O atoms 1.30 mol Fe / 1.30 = 1 × 3 = 3 Fe 1.73 mol O / 1.30 = 1.33 × 3 = 4 O Fe₃O₄ b.) 40.7% C, 5.0% H and 54.3% O (3) 40.7 g C × 1 mol C / 12.01 g C = 3.39 mol C 5.0 g H × 1 mol H / 1.01 g H = 4.95 mol H 54.3 g O × 1 mol O / 16.00 g O = 3.39 mol O 3.39 mol C / 3.39 = 1 × 2 = 2 C 4.95 mol H / 3.39 = 1.46 × 2 = 3 H 3.39 mol O / 3.39 = 1 × 2 = 2 O C₂H₃O₂ 2.) If the real molar mass of the compound in 2b.) is 110 g/mol, what is its molecular formula? (1) real molar mass / empirical mass = 110 / 59 = 2.00 C₂H₃O₂ × 2 = C₄H₆O₄