1. Empirical formulas 9.0 g of water consists of 1.0 g hydrogen and 8.0 g oxygen (11.1% hydrogen and 88.9% oxygen). Any mass of water will work so select a convenient mass of water and determine the mass and moles of hydrogen and oxygen atoms in that mass. What would be a convenient mass?

2. Empirical formulas Did you select 100 g (11.1 g hydrogen and 88.9 g oxygen)of water? Then you have 5.5mol of oxygen and 11.1 mol of hydrogen, and the empirical formula is: H 2n O n (n = 1,2,3, etc.) The molar mass of water is known to be 18.0g/mole, so the molecular formula is H 2 O (n=1)

3. Empirical formulas Calculate the % O and determine the empirical and molecular formulas. 1.Urea is 20.0%C, 6.7%H, 46.7%N and oxygen. with a molar mass of 60 g/mol. ANS: 26.6% O ANS: C n H 4n N 2n O n n=1 2. A student has an ion oxide sample (Which one?) that is 69.94% Fe with a molar mass of 160 g/mol. ANS: 30.06% O Fe 2n O 3n n=1

4. Empirical formulas Determine the % oxygen, empirical formula, and molecular formula for each of the following: PPPPP #%C%HMolar Mass Comment ANS: 1.52.513.0 46 g/molAlcohol in beer, whiskey, etc. C 2n H 6n O n n=1 2.38.79.6862 g/molEthylene Glycol-Used in antifreeze C n H 3n O n n=2 3.54.59.188 g/molButanoic (butyric) acid- foul odor C 2n H 4n O n n=2 4.26.14.346 g/molMethanoic (Formic) acid C n H 2n O 2n n=1 5.92.37.778 g/molBenzene Used in plastics (no oxygen) C n H n n=6 6.92.37.752 g/molCyclobutadiene (no oxygen) C n H n n=4 7.62.110.358 g/molPropanone (acetone) solvent C 3n H 6n O n n=1