1. stoichiometry
Moles to moles

2. Moles to Moles 2/2 = 2/x x = 2 moles of water will be made
2HCl + Ca(OH)2 => CaCl H2O
You have 50 moles of HCl, how much water can you make?
We balance the equation so you know how many moles of hydrochloric acid will react completely with how many moles of calcium hydroxide, in this case it is 2 moles of HCl for 2 moles of water.
Now set up a proportion between HCl and H2O the equation says that the ratio is 2:2 so
2/2 = 2/x x = 2 moles of water will be made

3. 2AlPO4+ + 3Ca(NO3)2 =. 2Al(NO3)3 + Ca3(PO4)2
You have 10 moles of aluminum phosphate, how many moles of calcium nitrate do you need to use all of it?
The proportion is 2/3 = 10/x x = 15 moles
If you have 6 moles of calcium nitrate, how many moles of calcium phosphate can you make?
3/1 = 6/x x = 2 moles of calcium phosphate

4. Grams to Grams Problems
You have 20 grams of sodium hydroxide reacting with excess hydrochloric acid. How much water and salt will you make? (in grams)

5. NaOH + HCl => H2O + NaCl
20g/40g/mol = .5 moles
1/.5 = 1/x x = .5 moles H2O
.5 moles X 18 g/mol = 9 grams of water
The proportion is the same for the salt, .5 moles so…
.5 moles X g/mol = grams NaCl

6. 2Al + 3H2SO4 => 3H2 + Al2(SO4)3 50 g / 98 g/mol = .51 moles
50 grams of sulfuric acid is reacted with aluminum. How much of each product do you make?
2Al + 3H2SO4 => 3H2 + Al2(SO4)3
50 g / 98 g/mol = .51 moles
3/.51 = 3/ x x = X 2 g/mol = grams
3/.51 = 1/x x = .17 moles X =58.14

7. Moles to grams
You have 20 moles of C2H6 that you burn. How many grams of CO2 do you make?
Balance the equation
2 C2H O2 => 4 CO2 + 6H2O
You have moles of ethane, so you can go directly to the proportion
The proportion is
2 / 20 = 4 / x x = 40 moles of CO2
You must convert this to grams so
Molar mass of CO2 is 44 g / mole
So X 40 = 1760 grams

8. Grams to Moles
You decompose 100 grams of iron (III) oxide into iron and oxygen. How many moles of each do you make?
Balance the equation
2Fe2O3 => 4Fe O2
You are given grams, so before you can set up a proportion, you must have moles, not grams
The molar mass for iron (III) oxide is
2 X X 16 = g / mole so…….
100 / = .63 moles
For iron the proportion is / .63 = 4 / x x = moles of Fe
For oxygen the proportion is 2 / .63 = 3 / x x = .95 moles of O

9. Practice problems
You have aluminum reacting with 50 grams of sodium hydroxide. How many moles of each product will you make?
You produce 500 grams of CO2 when you burn butane, C4H10. How many moles of oxygen must you have started with?
You decompose 40 grams of mercury(I) oxide. How many grams of mercury did you make? How many grams of oxygen?

10. Limiting reactants 2HCl + Ca(OH)2 => CaCl2 + 2H2O 100 75
100 grams of HCl reacts with 75 grams of Ca(OH)2
2HCl + Ca(OH) => CaCl H2O
100 75
Molar mass of HCl is = 36.5
100/36.5 = 2.74 moles
Molar mass of Calcium hydroxide is (1+16)X2 = 72.1
75/72.1 = 1.04 moles
Pick one and Set up a proportion 2/2.74 = 1/x x = 1.37 moles of calcium
Hydroxide is needed to use all of the hydrochloric acid, we have 1.04, calcium hydroxide is the limiting reactant

11. So use 1.04 moles of Ca(OH)2
2HCl + Ca(OH) => CaCl H2O
100 75
So set up a new proportion, solving first for how much calcium chloride you can make
1/1.04 = 1/x x = 1.04 moles CaCl2
Molar mass of CaCl2 is X = g
Do the same for water 1/1.04 = 2/x x = 2.08 moles X 18 = g water