1. Stoichiometry
mass and amount relationships between reactants and products in a chemical reaction

2. Rules for Solving Stoichiometry Problems
A balanced, properly written equation is essential because the coefficients tell you the mole to mole ratio.
Converting to moles is essential!

3. Example 1: If 2.50 moles of methane burns, how many moles of water vapor should be produced?
Step 1: Write a balanced equation. CH4 + 2O2  CO2 + 2H2O Step 2: What is the mole to mole ratio between methane and water? 1 mole CH4 : 2 moles H2O

4. Step 3: Apply the ratio to determine how many moles of water will be produced.
2.50 mol CH4 x 2 mol H2O = 5.00 mol H2O 1 1 mol CH4

5. Example 2: When CaC2 reacts with water, acetylene gas (C2H2) and calcium hydroxide are produced. How many grams of water are required to produce 1.55 moles of C2H2?
Step 1: Write a balanced equation.
CaC2 + 2H2O  C2H2 + Ca(OH)2

6. Step 2: Determine what info you have and what you are trying to determine.
You know you need to produce 1.55 moles of C2H2, and you need to determine how many grams of water are required to do this.

7. Step 3: What is the mole to mole ratio between the two. HINT
Step 3: What is the mole to mole ratio between the two? HINT! You determine this using the coefficients from the balanced equation.
moles of C2H2 : moles of H2O
1:2

8. Step 4: Apply the ratio to determine how many moles of water will be required.
1.55 mol C2H2 x 2 mol H2O = 3.10 mol H2O
1 1 mol C2H2

9. Step 5: The question asks for grams of H2O, so convert 3
Step 5: The question asks for grams of H2O, so convert 3.10 mol of H2O to grams.
3.10 mol H2O x g = 55.8 g H2O
mol H2O

10. REMEMBER! The ratio supplied by the coefficients of the balanced equation is a mole to mole ratio! It does not apply to grams!

11. Stoichiometry Practice
1. Determine the mass of lithium hydroxide produced when 3.80 moles of lithium nitride reacts with water according to the following equation:
Li3N + 3H2O  NH3 + 3LiOH
2. What mass of sodium chloride is produced when 0.45 g of chlorine reacts with excess sodium iodide?