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Percentage Yield and Energy Lesson 3. Sometimes reactions do not go to completion. Reaction can have yields from 1% to 100%. 1. How many grams of Fe are produced by the reaction of 100. g of Fe 2 O 3, if the percentage yield is 75.0%?. 2.
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Percentage Yield and Energy Lesson 3
Sometimes reactions do not go to completion.Reaction can have yields from 1% to 100%. 1. How many grams of Fe are produced by the reaction of 100. g of Fe2O3, if the percentage yield is 75.0%? 2 Fe2O3 + 3 C Fe + 3 CO2 4 100. g ? g = 52.4 g 100. g Fe2O3 x 1 mole x 4 mole Fe x 55.8 g x 0.750 159.6 g 2 mole Fe2O3 1 mole
Percentage Yield =Actual Yield x 100% Theoretical Yield Actual Yield is what is experimentally measured. Theoretical Yield is what is calculatedusing stoichiometry.
2. In an experiment 152. g of AgNO3 is used to make 75.1 g of Ag2SO4(s). Calculate the percentage yield. AgNO3(aq) + Na2SO4(aq) Ag2SO4(s) + 2NaNO3(aq) 75.1 g actual yield 2 1 152 g ? g 152. g AgNO3 x 1 mole x 1 Ag2SO4 x 311.9 g = 139.5 g 169.9 g 2 mole AgNO3 1 mole % yield = 75.1 x 100 % = 53.8 % 139.5
Energy Calculations • The energy term in a balanced equation can be used to calculate the amount of energy consumed or produced in a reaction. • How much energy is required to produce 25.4 g of H2? • + 2H2O H2 + O2 213 kJ 2 ? kJ 25.4 g 25.4 g H2 x 1 mole x 213 kJ = 1340 kJ 2.02 g 2 mole H2
4. How many molecules of H2 can be produced when 452 kJ of energy if consumed? 2 H2 + O2 2 H2O + 213 kJ 452 kJ ? Molecules x 6.02 x 1023 molecs 452 kJ x 2 moles H2 = 2.55 x 1024 molecs 213 kJ 1 mole
5. How much energy is produced by an explosion of a 5.2 L balloon full of hydrogen at STP? H2 + O22H2O + 213 kJ 2 5.2 L ? kJ x 213 kJ 5.2 L x 1 mole = 25 kJ 2 moles H2 22.4 L