StoichiometryStoichiometry

The MoleThe Mole A counting unitA counting unit

Similar to a dozen, except instead Similar to a dozen, except instead of 12, it’s of 12, it’s 602,000,000,000,000,000,000,000602,000,000,000,000,000,000,000

6.02 X 106.02 X 1023 23 (in scientific notation)(in scientific notation)

This number is named in honor of This number is named in honor of Amedeo Avogadro (1776 – 1856)Amedeo Avogadro (1776 – 1856)

The mass of 1 mole (in grams)The mass of 1 mole (in grams)

Equal to the numerical value from periodic Equal to the numerical value from periodic

table, or add the mass of the atoms together table, or add the mass of the atoms together

for a moleculefor a molecule

1 mole1 mole of C atoms of C atoms = = 12.0 g12.0 g

1 mole1 mole of Mg atoms of Mg atoms == 24.3 g24.3 g

11 mole mole of O of O22 molecules molecules == 32.0 g32.0 g

Molar MassMolar Mass

Molar Mass of CompoundsMolar Mass of Compounds

The molar mass (MM) of a compound is The molar mass (MM) of a compound is determined the same way, except you add up determined the same way, except you add up all the atomic masses for the molecule all the atomic masses for the molecule Ex. Molar mass of CaClEx. Molar mass of CaCl22Avg. Atomic mass of Calcium = 40.08gAvg. Atomic mass of Calcium = 40.08gAvg. Atomic mass of Chlorine = 35.45gAvg. Atomic mass of Chlorine = 35.45gMolar Mass of calcium chloride = Molar Mass of calcium chloride =

40.08 g/mol Ca + (2 X 35.45) g/mol Cl40.08 g/mol Ca + (2 X 35.45) g/mol Cl 110.98 g/mol CaCl 110.98 g/mol CaCl22

20

Ca  40.08 17

Cl 35.45

Formula UnitsFormula UnitsA term to describe an ionic or covalent A term to describe an ionic or covalent

compound.compound.

FlowchartFlowchart

Formula Units

Moles

Mass (grams)

Divide by 6.02 X 1023

Multiply by 6.02 X 1023

Multiply by atomic/molar mass from periodic tableDivide by

atomic/molar mass from periodic table

Atoms

Multiply by number of atoms in formula

Divide by number of atoms in formula

PracticePractice

Calculate the Molar Mass of Calculate the Molar Mass of calcium phosphatecalcium phosphate Formula = Formula = Masses elements:Masses elements:

Ca: 3 Ca’s X 40.1 = Ca: 3 Ca’s X 40.1 = P: 2 P’s X 31.0 = P: 2 P’s X 31.0 = O: 8 O’s X 16.0 = O: 8 O’s X 16.0 =

Molar Mass = Molar Mass =

Ca3(PO4)2

120.3 g

62.0 g

128.0 g

120.3g + 62.0g +128.0g310.3 g/mol

molar mass Avogadro’s numbermolar mass Avogadro’s number Grams Grams MolesMoles particles particles

Everything must go through Everything must go through Moles!!!Moles!!!

CalculationsCalculations

Atoms/Molecules and GramsAtoms/Molecules and Grams

How many moles of Cu are How many moles of Cu are present in 35.4 g of Cu?present in 35.4 g of Cu?

How many atoms would that be?How many atoms would that be?

Learning Check!Learning Check!

What is the mass (in grams) of What is the mass (in grams) of 1.20 X 101.20 X 102424 molecules of molecules of glucose (Cglucose (C66HH1212OO66)?)?

Hint: convert to moles first, Hint: convert to moles first, then to grams.then to grams.

PracticePractice

1. How many atoms in total are indicated in1. How many atoms in total are indicated in(a) NH(a) NH44NONO33 (b) Mg(b) Mg33(PO(PO44))22

2. How many formula units (molecules) are in 2. How many formula units (molecules) are in 3 moles of NH3 moles of NH44NONO33? How many atoms is that?? How many atoms is that?

3. How many moles are in 5.64 x 103. How many moles are in 5.64 x 102121 molecules molecules of Mgof Mg33(PO(PO44))22??

4.How many moles are in 9.52 x 104.How many moles are in 9.52 x 103131 atoms of atoms of MgMg33(PO(PO44))22??

Mass to atoms (and back)Mass to atoms (and back)

5. How many H atoms are in 2.3g of water?5. How many H atoms are in 2.3g of water?

6. Determine the mass of 6.7 x 106. Determine the mass of 6.7 x 101212 molecules of water.molecules of water.

7. Determine the number of atoms contained 7. Determine the number of atoms contained in 1.2 g of NaClin 1.2 g of NaCl

Complete Mole Calculations WorksheetComplete Mole Calculations WorksheetRead pg 47-50Read pg 47-50

Complete #5-11, pg 52Complete #5-11, pg 52

StoichiometryStoichiometry

Chocolate Chip Cookies!!Chocolate Chip Cookies!!1 cup butter

1/2 cup white sugar

1 cup packed brown sugar

1 teaspoon vanilla extract

2 eggs

2 1/2 cups all-purpose flour

1 teaspoon baking soda

1 teaspoon salt

2 cups semisweet chocolate chips

Makes 3 dozen

How many eggs are needed to make 3 dozen cookies?

How much butter is needed for the amount of chocolate chips used?

How many eggs would we need to make 9 dozen cookies?

How much brown sugar would I need if I had 1 ½ cups white sugar?

Cookies and Chemistry…Huh!?!?Cookies and Chemistry…Huh!?!?

Just like chocolate chip Just like chocolate chip cookies have recipes, cookies have recipes, chemists have recipes as wellchemists have recipes as well

Instead of calling them Instead of calling them recipes, we call them reaction recipes, we call them reaction equationsequations

Furthermore, instead of using Furthermore, instead of using cups and teaspoons, we use cups and teaspoons, we use molesmoles

Lastly, instead of eggs, butter, Lastly, instead of eggs, butter, sugar, etc. we use chemical sugar, etc. we use chemical compounds as ingredientscompounds as ingredients

Chemistry RecipesChemistry Recipes

You need a balanced reaction before you You need a balanced reaction before you start!start!

Ex: 2 Na + ClEx: 2 Na + Cl2 2 2 NaCl 2 NaClThis reaction tells us that by mixing 2 moles of Na This reaction tells us that by mixing 2 moles of Na

with 1 mole of Clwith 1 mole of Cl22we will get 2 moles of NaClwe will get 2 moles of NaCl

What if we wanted 4 moles of NaCl? 10 moles? What if we wanted 4 moles of NaCl? 10 moles? 50 moles?50 moles?

PracticePractice

Write the balanced rxn for hydrogen gas reacting Write the balanced rxn for hydrogen gas reacting with oxygen gas to produce waterwith oxygen gas to produce water

2 H2 H22 + O + O22 2 H 2 H22OO Moles of reactants are needed?Moles of reactants are needed? What if we wanted 4 moles of water?What if we wanted 4 moles of water? If we had 3 moles of OIf we had 3 moles of O22, how much H, how much H22 would we need? would we need?

How much water would we get?How much water would we get?

If we had 50 moles of hydrogen, how much oxygen would If we had 50 moles of hydrogen, how much oxygen would we need? How much water produced? we need? How much water produced?

2 mol H2 1 mol O2

4 mol H2

2 mol O2

6 mol H2, 6 mol H2O

25 mol O2, 50 mol H2O

Mole RatiosMole Ratios

Mole ratios can be used to calculate the moles Mole ratios can be used to calculate the moles of one chemical from the given amount of a of one chemical from the given amount of a different chemical different chemical

Ex: How many moles of ClEx: How many moles of Cl22 are needed to react are needed to react

with 5 moles of Na (using all the Na)?with 5 moles of Na (using all the Na)?

2 Na + Cl2 Na + Cl22 2 NaCl 2 NaCl

5 moles Na 1 mol Cl2

2 mol Na= 2.5 moles Cl2

Mole-Mole ConversionsMole-Mole ConversionsHow many moles of NaCl will be produced How many moles of NaCl will be produced

if you react 2.6 moles of Clif you react 2.6 moles of Cl22 with an with an

excess of Na?excess of Na?

2 Na + Cl2 Na + Cl22 2 NaCl 2 NaCl

2.6 moles Cl2 2 mol NaCl

1 mol Cl2= 5.2 moles NaCl

Mole-Mass ConversionsMole-Mass Conversions

Amounts of a chemical are often given in grams Amounts of a chemical are often given in grams instead of molesinstead of moles

We still go through moles and use the mole ratio, We still go through moles and use the mole ratio, but now we also use molar mass to get to gramsbut now we also use molar mass to get to grams

Ex: How many grams of ClEx: How many grams of Cl22 are required to react are required to react

completely with 5.00 moles of Na to produce NaCl?completely with 5.00 moles of Na to produce NaCl?

2 Na + Cl2 Na + Cl22 2 NaCl 2 NaCl

5.00 moles Na 1 mol Cl2 70.90g Cl2

2 mol Na 1 mol Cl2

= 177g Cl2

You PracticeYou Practice

Calculate the mass in grams of iodine Calculate the mass in grams of iodine required to react completely with 0.50 required to react completely with 0.50 moles of Al.moles of Al.

2 Al + 3 I2 Al + 3 I2 2 2 AlI 2 AlI3 3

Mass-MoleMass-MoleWe can also start with mass and convert to We can also start with mass and convert to

moles of product or another reactantmoles of product or another reactantWe use molar mass and the mole ratio to get We use molar mass and the mole ratio to get

to moles of the compound of interestto moles of the compound of interestCalculate the number of moles of ethane (CCalculate the number of moles of ethane (C22HH66) )

needed to produce 10.0 g of waterneeded to produce 10.0 g of water 2 C2 C22HH66 + 7 O + 7 O22 4 CO 4 CO22 + 6 H + 6 H220 0

10.0 g H2O 1 mol H2O 2 mol C2H6

18.0 g H2O 6 mol H20

= 0.185 mol C2H6

Mass-Mass ConversionsMass-Mass Conversions

Most often we are given a starting mass Most often we are given a starting mass and want to find out the mass of a product and want to find out the mass of a product (called theoretical yield) or how much of (called theoretical yield) or how much of another reactant we need to completely another reactant we need to completely react with it (no leftovers!)react with it (no leftovers!)

Steps for Mass to MassSteps for Mass to Mass

1.1. Grams to moles of given substanceGrams to moles of given substance

2.2. Mole ratioMole ratio

3.3. Moles to grams of compound Moles to grams of compound

Mass-Mass ConversionMass-Mass Conversion

Ex. Calculate how many grams of Ex. Calculate how many grams of ammonia are produced when you react ammonia are produced when you react 2.00g of nitrogen with excess hydrogen.2.00g of nitrogen with excess hydrogen.

NN2 2 + 3 H+ 3 H2 2 2 NH 2 NH33

2.00g N2 1 mol N2 2 mol NH3 17.06g NH3

28.02g N2 1 mol N2 1 mol NH3

= 2.4 g NH3

Read pg 110-114Read pg 110-114

Do: #4-7 pg 115Do: #4-7 pg 115

#9 & 10 pg 117#9 & 10 pg 117

19 & 20 pg 12519 & 20 pg 125

#Check your answers on pg 151#Check your answers on pg 151

PracticePractice

How many grams of calcium nitride are How many grams of calcium nitride are produced when 2.00 g of calcium reacts produced when 2.00 g of calcium reacts with an excess of nitrogen?with an excess of nitrogen?

Practice Practice

Given the equation C + OGiven the equation C + O22 CO CO

(a)(a) Balance the equationBalance the equation

(b)(b) How many moles of OHow many moles of O22 are required to are required to react with 2.36 moles of C?react with 2.36 moles of C?

(c)(c) How many moles of CO will be formed How many moles of CO will be formed from 5.9 moles of C reacting?from 5.9 moles of C reacting?