1. Recall: A limiting reagent is the reactant whose entities are completely consumed in a reaction. It is the one that runs out first, and as a result, stops the reaction. An excess reagent is any reactant that is left over at the conclusion of the reaction. Calculating Mass of Excess Reagents HOW MUCH REAGENT IS ENOUGH TO BE EXCESS ?? Rule of thumb: Do stoichiometry to calculate the minimum mass required, then add 10%.

2. You decide to test the method of stoichiometry using the reaction of 2.00 g of copper (II) sulfate in solution with an excess of sodium hydroxide in solution. What would be a reasonable mass of sodium hydroxide to use? 1.10 g NaOH (aq)

3. Identifying Limiting and Excess Reagents Identify the limiting reagent by: 1) converting each reagent to chemical amount (i.e. number of moles) 2) using the mole ratio to compare the required amount of the other reagent with the amount actually present The excess reagent is the one that is not the limiting reagent (duh). If 10.0 g of copper is placed in a solution of 20.0 g of silver nitrate, which reagent will be the limiting reagent? AgNO 3 (aq)

4. In the reaction of a 10.0 g sample of copper with 20.0 g of silver nitrate in solution, what mass of copper will be in excess? What mass of silver will be produced? = 0.118 mol (from previous example) 6.3 g excess copper 12.7 g silver

5. In an experiment, 26.8 g of iron (III) chloride in solution is combined with 21.5 g of sodium hydroxide in solution. Which reactant is in excess, and by how much? What mass of each product will be obtained? 1.7 g excess NaOH (aq) 17.7 g Fe(OH) 3 (s) 29.0 g NaCl (aq)

6. Another Example If 10.1 g of magnesium and 2.87 g of hydrogen chloride gas are reacted, what is the limiting reagent? How much excess reagent remains? How many grams of gas will be produced? 10.1 g2.87 g 24.31 g/mol m 36.46 g/mol limiting reagent is HCl (g) 9.04 g excess Mg (s) 0.0795 g H 2 (g) 2.02 g/mol

7. Yet Another Example If 10.3 g of aluminum are reacted with 51.7 g of aqueous copper (II) sulfate, how much copper will be produced? How much excess reagent will remain? 10.3 g51.7 g 26.98 g/mol m 159.62 g/mol63.55 g/mol 4.48 g excess Al (s) 20.6 g Cu (s)

8. Read pgs. 320 – 324 pgs. 321, 324 Practice #’s 1 – 5 pg. 327 Section 8.3 Questions #’s 1 – 9