Proportional Relationships : Proportional Relationships 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 eggs 5 doz.
2 eggs = 12.5 dozen cookies Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Proportional Relationships : Proportional Relationships Stoichiometry
mass relationships between substances in a chemical reaction
based on the mole ratio
Mole Ratio
indicated by coefficients in a balanced equation 2 Mg + O2 ? 2 MgO Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Stoichiometry Steps : Stoichiometry Steps 1. Write a balanced equation.
2. Identify known & unknown.
3. Line up conversion factors.
Mole ratio - moles ? moles
Molar mass - moles ? grams
Molarity - moles ? liters soln
Molar volume - moles ? liters gas Core step in all stoichiometry problems!! Mole ratio - moles ? moles 4. Check answer. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Molar Volume at STP : 1 mol of a gas=22.4 L
at STP Molar Volume at STP Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Molar Volume at STP : Molar Volume at STP Molar Mass
(g/mol) 6.02 ? 1023
particles/mol MASS
IN
GRAMS MOLES NUMBER
OF
PARTICLES LITERS
OF
SOLUTION Molar Volume
(22.4 L/mol) LITERS
OF GAS
AT STP Molarity (mol/L) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Stoichiometry Problems : Stoichiometry Problems How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O2 2 mol KClO3
3 mol O2 = 6 mol KClO3 2KClO3 ? 2KCl + 3O2 ? mol 9 mol Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Stoichiometry Problems : How many grams of KClO3 are req’d to produce 9.00 L of O2 at STP? 9.00 L
O2 1 mol
O2
22.4 L
O2 = 32.8 g
KClO3 2 mol
KClO3
3 mol
O2 122.55
g KClO3
1 mol
KClO3 ? g 9.00 L Stoichiometry Problems 2KClO3 ? 2KCl + 3O2 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Stoichiometry Problems : Stoichiometry Problems How many grams of silver will be formed from 12.0 g copper? 12.0
g Cu 1 mol
Cu
63.55
g Cu = 40.7 g
Ag Cu + 2AgNO3 ? 2Ag + Cu(NO3)2 2 mol
Ag
1 mol
Cu 107.87
g Ag
1 mol
Ag 12.0 g ? g Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Stoichiometry Problems : 63.55
g Cu
1 mol
Cu Stoichiometry Problems How many grams of Cu are required to react with 1.5 L of 0.10M AgNO3? 1.5
L .10 mol
AgNO3
1 L = 4.8 g
Cu Cu + 2AgNO3 ? 2Ag + Cu(NO3)2 1 mol
Cu
2 mol
AgNO3 ? g 1.5L
0.10M Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem