Bellwork What is the mass of one mole of hydrogen peroxide, H2O2? What is the mass of ten moles of hydrogen peroxide?

CHAPTER 7 THE MOLE

CALCULATING EMPIRICAL FORMULAS Empirical formula - lowest whole number ratio of the elements in a compound - may or may not be the same as the molecular formula.

Steps to calculate empirical formula: 1. Find moles of each element. 2 Steps to calculate empirical formula: 1. Find moles of each element. 2. Set up mole ratio. 3. Simplify mole ratio (divide by smallest). If your answers are not in whole numbers, you must multiply by 2,3,4,or 5 to get whole numbers. 4. Use mole ratio as subscripts in the formula. If given % composition, assume 100 g of compound.

Empirical Formula Poem Percent to mass, mass to moles, divide by smallest and round ‘till whole!

A compound is 79.8% C and 20.2% H. Find its empirical formula.

A compound is 79.8% C and 20.2% H. Find its empirical formula. /6.65 = 1 79.8gC 1mol C = 6.65 mol C 12.0 g C 20.2 g H 1 mol H = 20.0 mol H 1.01 g H CH3 /6.65 = 3

Find the empirical formula for a compound made up of 26. 7% P, 12 Find the empirical formula for a compound made up of 26.7% P, 12.1% N and 61.2% Cl.

Find the empirical formula for a compound made up of 26. 7% P, 12 Find the empirical formula for a compound made up of 26.7% P, 12.1% N and 61.2% Cl. 26.7 g P 1 mol P = 0.861 mol P 31.0 g P 12.1 g N 1 mol N = 0.864 mol N 14.0 g N 61.2 g Cl 1 mol Cl = 1.72 mol Cl 35.5 g Cl /0.861=1 /0.861=1 /0.861=2 Empirical Formula = PNCl2