1. The Mole & Stoichiometry!

2. Important Conversion Factors
1 mole
= 6.021023 molecules or atoms
= molar mass in grams
= 22.4 L

3. Mole Conversions How many grams are in 2.5 moles of CO2?
2.5 mol CO g = 110 g CO2
1 mol

4. Molar Ratios For reaction calculations, the molar ratio is used.
Example:
How many moles of nitrogen are needed to react with 9 moles of hydrogen?
2N2(g) +3 H2(g) → 3NH3(g)
Given: 9 moles H2, Find moles N2
9 mol H2 x
2 mol N2
= 6 mol N2
3 mol H2
Mole ratio

5. Stoichiometry Example
How many grams of nitrogen are needed to react with 2.0 grams of hydrogen?
2N2(g) +3 H2(g) → 3NH3(g)
Given: 2.0 grams H2, Find grams N2
2.0 g H2 x
1 mol H2
2 mol N2
28.0 g N2
= g N2
3 mol H2
1 mol N2

6. Stoichiometry Example
For reaction calculations, the molar ratio is used.
Example 2:
How many grams of nitrogen are needed to react with 2.0 grams of hydrogen using this equation?
2N2(g) +3 H2(g) → 3NH3(g)
Given: 2.0 grams H2, Find grams N2
2.0g H2
x g N2
3(2g)
2 (28g) =

7. Limiting and Excess Reactants
Limiting Reactant - limits the amount of product that can be formed and is completely consumed.
Excess Reactant - left over when reaction ends

8. Formulas Empirical : gives the simplest ratio of atoms
Molecular: gives the actual number of atoms