# Stoichiometry Chap. 12. I.What is stoichiometry? Study of quantitative relationships between amounts of reactants and products.

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Stoichiometry Chap. 12

I.What is stoichiometry? Study of quantitative relationships between amounts of reactants and products

I.What is stoichiometry? Mass is conserved during a chemical reaction. A.Stoichiometry is based on Lavoisier’s Law

I.What is stoichiometry? Coefficients give an important information for calculation A.Stoichiometry is based on Lavoisier’s Law B.Uses a balanced equation

Al 2 O 3 + C Al + CO 2 Coefficients in Equation

Al 2 O 3 + C Al + CO 2 Coefficients in Equation 2334

Al 2 O 3 + C Al + CO 2 Coefficients in Equation 2334 2 formula units 3 atoms 4 atoms 3 molecules

Al 2 O 3 + C Al + CO 2 Coefficients in Equation 2334 2 moles 3 moles 4 moles 3 moles

I.What is stoichiometry? A.Stoichiometry is based on Lavoisier’s Law B.Uses a balanced equation C.Involves mole conversions

I.What is stoichiometry? A.Stoichiometry is based on Lavoisier’s Law B.Uses a balanced equation C.Involves mole conversions 1.grams moles

I.What is stoichiometry? A.Stoichiometry is based on Lavoisier’s Law B.Uses a balanced equation C.Involves mole conversions 1.grams moles 2.particles moles

I.What is stoichiometry? A.Stoichiometry is based on Lavoisier’s Law B.Uses a balanced equation C.Involves mole conversions 1.grams moles 2.particles moles 3.liters moles

II. Mole to Mole ratio

A.Comes from equation

H 2 + O 2 H 2 O Coefficients in Equation

H 2 + O 2 H 2 O Coefficients in Equation 212 2 moles 1 mole2 moles

H 2 + O 2 H 2 O Coefficients in Equation 212 2 moles 1 mole2 moles 2 mol H 2 1 mol O 2 2 mol H 2 2 mol H 2 O 1 mol O 2 2 mol H 2 O some mole ratios from this equation:

II. Mole to Mole ratio A.Comes from equation B.Calculations

Self Check – Ex. 1 2C + O 2 2CO How many moles of oxygen are required to react with 4.2 moles of carbon?

Self Check – Ex. 2 2C + O 2 2CO How many moles of carbon monoxide can be formed when 3 moles of oxygen react?

III. Stoichiometry Calculations

A.Gram to grams

Self Check – Ex. 3 2C + O 2 2CO How many grams of carbon monoxide can be formed when 96 grams of oxygen react?

III. Stoichiometry Calculations A.Gram to grams B.Grams to molecules

Self Check – Ex. 4 CaCl 2 + 2 AgNO 3 Ca(NO 3 ) 2 + 2AgCl How many formula units of silver chloride are formed when 111 g of calcium chloride react?

III. Stoichiometry Calculations A.Gram to grams B.Grams to molecules C.Grams to liters

Self Check – Ex. 5 Zn + HNO 3 H 2 + Zn(NO 3 ) 2 How many liters of hydrogen gas at STP could be formed when 6.00 g of zinc reacts with nitric acid?

IV. Limiting Reactants How do you ‘turn off’ a chemical reaction?

IV. Limiting Reactants A.Terms

IV. Limiting Reactants A.Terms 1.Limiting reactant Substance that runs out first in a chemical reaction, thus limits the amount of product.

IV. Limiting Reactants A.Terms 1.Limiting reactant 2.Excess reactant Reactant that is present in excess, thus is left over when a reaction stops.

IV. Limiting Reactants A.Terms B.An analogy

The following parts are used to make trikes: WheelsFramePedals Symbol: W Requirement: 3 Symbol: F Requirement: 1 Symbol: P Requirement: 2

What is the ‘chemical formula’ for this trike?

W 3 FP 2

Write the ‘balanced equation’ for trike-making.

3 W + 1 F + 2 P W 3 FP 2 ++

How much product (trikes) could you make with: Supplies 24 wheels 10 frames 14 pedals

IV. Limiting Reactants A.Terms B.An analogy C.A chemical example

How many grams of product can you make with: Supplies 28 g N 2 18 g H 2 N 2 + 3H 2 2 NH 3

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 + 1H 2 O 2NaOH + 2H 2 If 23.0 g of sodium reacts with 9.0 g of water, what mass of hydrogen gas is formed?

Self Check – Ex. 7 1Fe 2 O 3 + 3H 2 2Fe + 3H 2 O 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?

V. Percent Yield A value that tells how ‘successful’ a reaction is at making product.

V. Percent Yield A.Theoretical yield The mass of product that can be formed in a reaction (calculated value)

V. Percent Yield A.Theoretical yield B.Actual yield The mass of product that is produced in a reaction (measured by experiment)

V. Percent Yield A.Theoretical yield B.Actual yield C.Percent Yield Actual yield Theoretical yield x 100 Percent yield =

V. Percent Yield C.An analogy

V. Percent Yield C.An analogy What is the percent yield? 30 kernels

What is the percent yield? 30 kernels Actual yield Percent yield = Theoretical yield

What is the percent yield? 30 kernels Actual yield Percent yield = Theoretical yield = 30

What is the percent yield? 30 kernels Actual yield = 24 Percent yield = Theoretical yield = 30 24 popped corn

What is the percent yield? 30 kernels Actual yield = 24 Percent yield = Theoretical yield = 30 24 popped corn = 75%

V. Percent Yield A.Theoretical yield B.Actual yield C.Percent Yield D.An analogy E.Examples

Self Check – Ex. 8 2Ca + 2H 2 O 2Ca(OH) 2 + 1H 2 When 10.0 g of calcium reacts with excess water, 15.0 g of calcium hydroxide is recovered. What is the percent yield?

The end.

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