Stoichiometry

Proportional Relationships b I have 5 eggs. How many cookies can I make? 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 5 eggs5 doz. 2 eggs = 12.5 dozen cookies Ratio of eggs to cookies x

Proportional Relationships b Stoichiometry mass relationships between substances in a chemical reaction based on the mole ratio b Mole Ratio indicated by coefficients in a balanced equation 2 Mg + O 2  2 MgO

Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Line up conversion factors. Mole ratio - moles  moles Molar mass -moles  grams 4. Cancel units. 5. Multiply across top & bottom. 6. Final divide.

Stoichiometry Problems b How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3  2KCl + 3O 2 ? mol9 mol x

Stoichiometry Problems b How many grams of CuO are needed to produce 4 moles H 2 O? 4 mol H 2 O g CuO 1 mol CuO = g CuO CuO + 2HCl  CuCl 2 + H 2 O ? g 4 moles 1 mol CuO 1 mol H 2 O x x

Stoichiometry Problems b How many grams of silver will be formed from 12.0 g copper? 12.0 g Cu g Ag 1 mol Ag = 40.7 g Ag Cu + 2AgNO 3  2Ag + Cu(NO 3 ) g? g 2 mol Ag 1 mol Cu 1 mol Cu g Cu xx x

Stoichiometry Problems b How many grams of ammonia will be formed from 5.40 g of hydrogen? 5.40 g H g NH 3 1 mol NH 3 = g NH 3 N 2 + H 2  NH g? g 2 mol NH 3 3 mol H 2 1 mol H g H 2 xx x 3 2