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

2. Rules for Solving Stoichiometry Problems 1. A balanced, properly written equation is essential because the coefficients tell you the mole to mole ratio. 2. Converting to moles is essential!

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

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

5. 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 C 2 H 2 : moles of H 2 O 1:2

6. Step 4: Apply the ratio to determine how many moles of water will be required. 1.55 mol C 2 H 2 x2 mol H 2 O=3.10 mol H 2 O 11 mol C 2 H 2

7. Step 5: The question asks for grams of H 2 O, so convert 3.10 mol of H 2 O to grams. 3.10 mol H 2 Ox 18.0 g =55.8 g H 2 O 1 1 mol H 2 O

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

9. 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: Li 3 N + 3H 2 O  NH 3 + 3LiOH 2. What mass of sodium chloride is produced when 0.45 g of chlorine reacts with excess sodium iodide?