I. I.Stoichiometric Calculations Stoichiometry

History of Stoichiometry b Comes from the Greek: Stoicheion - to measure the elements

History of Stoichiometry Joseph Black and Daniel Rutherford studied the reaction CaCO 3 CaO + CO 2 They were looking at how the mass was changing in the reaction. They realized there the relation in the changing mass was actually in moles of substance.

Proportional Relationships b Stoichiometry mass relationships between substances in a chemical reaction based on the mole ratio b Mole Ratio indicated by coefficients in a balanced equation 2 Mg + O 2  2 MgO

Stoichiometry Problems b How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3  2KCl + 3O 2 ? mol9 mol

Stoichiometry Problems b How many moles of KCl are produced when 3.6 mol of KCLO 3 are decomposed? 3.6 mol KClO 3 2 mol KCl 2 mol KClO 3 = 7.2 mol KCl 2KClO 3  2KCl + 3O 2 ? mol 3.6 mol

Stoichiometry Problems b Do Mole to Mole WS

Stoichiometry Steps Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Line up conversion factors. Mole ratio - moles  moles Molar mass -moles  grams Molarity - moles  liters soln Molar volume -moles  liters gas Core step in all stoichiometry problems!! Mole ratio - moles  moles 4. Check answer.

1 mol of a gas=22.4 L at STP Molar Volume at STP Molar Volume at STP S tandard T emperature & P ressure 0°C and 1 atm

“Stoich – nid”

Stoichiometry Problems b How many grams of silver will be formed when 12.0 g copper react with excess aqueous silver nitrate? 12.0 g Cu 1 mol Cu g Cu = 40.7 g Ag Cu + 2AgNO 3  2Ag + Cu(NO 3 ) 2 2 mol Ag 1 mol Cu g Ag 1 mol Ag 12.0 g? g

63.55 g Cu 1 mol Cu Stoichiometry Problems b How many grams of Copper atoms are required to react completely with 1.5 x formula units of AgNO 3 ? 1.5 x Form units AgNO 3 1mol AgNO x Form units AgNO 3 = 7.9 g Cu Cu + 2AgNO 3  2Ag + Cu(NO 3 ) 2 1 mol Cu 2 mol AgNO 3 ? g 1.5 x form units

b How many grams of KClO 3 are req’d to produce 9.00 L of O 2 at STP? 9.00 L O 2 1 mol O L O 2 = 32.8 g KClO 3 2 mol KClO 3 3 mol O g KClO 3 1 mol KClO 3 ? g9.00 L Stoichiometry Problems 2KClO 3  2KCl + 3O 2

Stoichiometry Problems b Do Stoich WS 1