1. Stoichiometry Chapter 9 Mass calculations Stoich ppt _2 mass-mass

2. Stoichiometry After this presentation, you should understand:  Review: Moles, mass, representative particles (atoms, molecules, formula units), molar mass, and Avogadro’s number.  Calculations using balanced chemical equations: for example, for a given mass of a reactant, calculate the mass of product formed.

3. Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Line up conversion factors. – Mole ratio - moles  moles – Molar mass -moles  grams – Molar volume -moles  liters gas This is the new one –from the balanced equation. The key step in stoichiometry! 4. Check answer, units, significant figures.

4. Stoichiometry Island Diagram Mass Particles VolumeMole Mass Known Unknown Substance A Substance B Stoichiometry Island Diagram Volume Particles M V P Mass Mountain Liter Lagoon Particle Place Mole Island

5. Stoichiometry Island Diagram Mass Particles Volume Mole Mass Volume Particles Known Unknown Substance A Substance B Stoichiometry Island Diagram 1 mole = molar mass (g) Use coefficients from balanced chemical equation 1 mole = 22.4 L @ STP 1 mole = 6.022 x 10 23 particles (atoms or molecules) 1 mole = 22.4 L @ STP 1 mole = 6.022 x 10 23 particles (atoms or molecules) 1 mole = molar mass (g) (gases)

6. Time to Practice! Grab your calculator and periodic table.

7. How many grams of KClO 3 must decompose in order to produce 9.0 moles of oxygen gas? 9.0 mol O 2 2 mol KClO 3 3 mol O 2 = 740 g KClO 3 2KClO 3  2KCl + 3O 2 ? g9.0 mol O2O2 KClO 3 740 g 122.55 g KClO 3 1 mol KClO 3

8. How many grams of KClO 3 are required to produce 9.00 g of O 2 ? 9.00 g O 2 1 mol O 2 32.00 g O 2 = 23.0 g KClO 3 2 mol KClO 3 3 mol O 2 122.55 g KClO 3 1 mol KClO 3 ? g9.00 g 2KClO 3  2KCl + 3O 2 O2O2 KClO 3 23.0 g

9. 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 1 Cu + 2 AgNO 3  2 Ag + 1 Cu(NO 3 ) 2 2 mol Ag 1 mol Cu 107.87 g Ag 1 mol Ag 12.0 g? g CuAg 40.7 g