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Stoichiometry. Chap. 12. What is stoichiometry?. Study of quantitative relationships between amounts of reactants and products. What is stoichiometry?. Stoichiometry is based on Lavoisier’s Law. Mass is conserved during a chemical reaction. What is stoichiometry?.
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Stoichiometry Chap. 12
What is stoichiometry? Study of quantitative relationships between amounts of reactants and products
What is stoichiometry? • Stoichiometry is based on Lavoisier’s Law Mass is conserved during a chemical reaction.
What is stoichiometry? • Stoichiometry is based on Lavoisier’s Law • Uses a balanced equation Coefficients give an important information for calculation
Coefficients in Equation Al2O3 + C Al + CO2
Coefficients in Equation Al2O3 + C Al + CO2 2 3 4 3
Coefficients in Equation Al2O3 + C Al + CO2 2 3 4 3 2 formula units 4 atoms 3 molecules 3 atoms
Coefficients in Equation Al2O3 + C Al + CO2 2 3 4 3 2 moles 4 moles 3 moles 3 moles
What is stoichiometry? • Stoichiometry is based on Lavoisier’s Law • Uses a balanced equation • Involves mole conversions
What is stoichiometry? • Stoichiometry is based on Lavoisier’s Law • Uses a balanced equation • Involves mole conversions • grams moles
What is stoichiometry? • Stoichiometry is based on Lavoisier’s Law • Uses a balanced equation • Involves mole conversions • grams moles • particles moles
What is stoichiometry? • Stoichiometry is based on Lavoisier’s Law • Uses a balanced equation • Involves mole conversions • grams moles • particles moles • liters moles
Mole to Mole ratio • Comes from equation
Coefficients in Equation H2 + O2 H2O
Coefficients in Equation H2 + O2 H2O 2 1 2 2 moles 1 mole 2 moles
Coefficients in Equation H2 + O2 H2O 2 1 2 2 moles 1 mole 2 moles some mole ratios from this equation: 2 mol H2 2 mol H2 1 mol O2 1 mol O2 2 mol H2O 2 mol H2O
Mole to Mole ratio • Comes from equation • Calculations
Self Check – Ex. 1 2C + O2 2CO How many moles of oxygen are required to react with 4.2 moles of carbon?
Self Check – Ex. 2 2C + O2 2CO How many moles of carbon monoxide can be formed when 3 moles of oxygen react?
Stoichiometry Calculations • Gram to grams
Self Check – Ex. 3 2C + O2 2CO How many grams of carbon monoxide can be formed when 96 grams of oxygen react?
Stoichiometry Calculations • Gram to grams • Grams to molecules
Self Check – Ex. 4 CaCl2 + 2 AgNO3 Ca(NO3)2 + 2AgCl How many formula units of silver chloride are formed when 111 g of calcium chloride react?
Stoichiometry Calculations • Gram to grams • Grams to molecules • Grams to liters
Self Check – Ex. 5 Zn + HNO3 H2 + Zn(NO3)2 How many liters of hydrogen gas at STP could be formed when 6.00 g of zinc reacts with nitric acid?
Limiting Reactants How do you ‘turn off’ a chemical reaction?
Limiting Reactants • Terms
Limiting Reactants • Terms • Limiting reactant Substance that runs out first in a chemical reaction, thus limits the amount of product.
Limiting Reactants • Terms • Limiting reactant • Excess reactant Reactant that is present in excess, thus is left over when a reaction stops.
Limiting Reactants • Terms • An analogy
The following parts are used to make trikes: Wheels Frame Pedals Symbol: W Requirement: 3 Symbol: F Requirement: 1 Symbol: P Requirement: 2
Write the ‘balanced equation’ for trike-making. 3 W + 1 F + 2 P W3FP2 + +
How much product (trikes) could you make with: Supplies 24 wheels 10 frames 14 pedals
Limiting Reactants • Terms • An analogy • A chemical example
How many grams of product can you make with: Supplies 28 g N2 18 g H2 N2 + 3H2 2 NH3
Recognizing a limiting reactant problem: There are two ‘givens’
Solving a limiting reactant problem: Do two calculations, and pick the reactant that makes the smaller amount of product.
Self Check – Ex. 6 2Na + 1H2O 2NaOH + 2H2 If 23.0 g of sodium reacts with 9.0 g of water, what mass of hydrogen gas is formed?
Self Check – Ex. 7 1Fe2O3 + 3H22Fe + 3H2O If 85.5 g of iron (III) oxide reacts with 15.7 g of hydrogen, what mass of iron is formed? What is the limiting reactant?
Percent Yield A value that tells how ‘successful’ a reaction is at making product.
Percent Yield • Theoretical yield The mass of product that can be formed in a reaction (calculated value)
Percent Yield • Theoretical yield • Actual yield The mass of product that is produced in a reaction (measured by experiment)
Percent Yield • Theoretical yield • Actual yield • Percent Yield Actual yield x 100 Percent yield = Theoretical yield