1. 9-3 Compounds and Moles *C 2 H 6 O 2 means there are 2 moles of carbon, 6 moles of hydrogen, and 2 moles of oxygen…(In one mole of the compound.)… *…or a mole ratio of 2:6:2

2. 3-step problems When neither your unknown or known is moles, you have a 3-step problem... Use the same rules for dimensional analysis, but keep writing until you have 3 blanks before the answer. Example...How many molecules are found in 3.0 moles of O 2 ?

3. Molar Volume Every gas, at STP, has a volume of 22.4 L. STP is standard temperature and pressure. STP conditions are 0 C and 1 atm. Example....How many liters of volume are 3.0 moles of helium?

4. 9-4 Empirical and Molecular Formula An empirical formula is a most reduced formula. The molecular formula is the actual formula. 1.To solve, first take % and convert to grams...(quantities may start in grams.) 2.Convert grams to moles. 3.Divide all mole values by the smallest to reduce the ratio. 4.If the ratio is not in whole number values multiply to make them whole numbers.

5. Molecular Formula 1. Start with an empirical formula. 2. Add up the molar mass of the empirical formula. 3. Divide the mass of the molecular formula by the mass of the empirical formula. 4. Multiply all of the subscripts by the answer from #3.

6. % Composition You will get a molecular or ionic formula and add up the molar mass. Divide the mass of each element by the total molar mass and multiply by 100. You can also be given the mass of the elements instead of a formula... Examples...What is the % compostion of H 2 O? What is the % compostion if a compound has 2.5 grams of hydrogen and 7.5 grams of carbon?

7. Hydrates CuSO 4. 5 H 2 O copper (II) sulfate penta hydrate To calculate the % water in a hydrate divide the weight of the water by the total compound weight, then multiply by 100.