Catalyst:

1

Catalyst:Balance the following chemical equation.

 Pb(NO3)2 + AlCl3 → PbCl2 + Al(NO3)3

New seats on front boardObjectives:Calculate the moles or grams of a substances in a given equation.Determine the percent composition of elements in a compound.

Homework:C.7/C.10 worksheet

2

Warm-up

Balance the following chemical equation. 

Pb(NO3)2 + AlCl3 → PbCl2 + Al(NO3)3

1 Pb 12 NO3 3

1 Al 13 Cl 2

3

Warm-up

Balance the following chemical equation. 

3 Pb(NO3)2 + AlCl3 → PbCl2 + 2 Al(NO3)3

3 Pb 16 NO3 6

1 Al 23 Cl 2

4

Warm-up

Balance the following chemical equation. 

3 Pb(NO3)2 + 2 AlCl3 → 3 PbCl2 + 2 Al(NO3)3

3 Pb 36 NO3 6

2 Al 26 Cl 6

Converting grams to moles

To convert grams to moles:• Write down your given amount of grams.• Calculate the molar mass.• Put the grams part of the molar mass on

bottom, put the moles part (1 mol) on top.

Converting grams to moles

Ex:• How many moles is 50 grams of magnesium?

• 270 grams of methanol (CH3OH) is how many moles?

Converting moles to grams

To convert moles to grams:• Write down your given amount of moles.• Calculate the molar mass.• Put the grams part of the molar mass on top,

put the moles part (1 mol) on bottom.

Converting moles to grams

Ex:• How many grams is 3 moles of gold?

• .6 moles of baking soda (NaHCO3) is how many grams of baking soda?

Equations and Molar Relationships

CuO (s) + C(s) → Cu(s) + CO2

2 CuO (s) + C(s) → 2 Cu(s) + CO2

2 CuO (s) + C(s) → 2 Cu(s) + CO2

2 formula units CuO

1 atom C 2 atoms Cu 1 molecule CO2

2 mol CuO 1 mol C 2 mol Cu 1 mol CO2

2 CuO (s) + C(s) → 2 Cu(s) + CO2

2 mol CuO = 2 mol Cu2 mol CuO = 1 mol CO2

2 mol CuO = 1 mol C1 mol C = 2 mol Cu1 mol C = 1 mol CO2

2 mol Cu = 1 mol CO2

These will be your conversion factors.

Review & Examples

We have two main places to get conversion factors:• Molar mass (grams <-> moles)• Coefficients (moles <-> moles)

Problem Solving Flow Chart

Use molar mass of X; calculate it using info from periodic table.

Use coefficients from balanced equation.

Use molar mass of Y; calculate it using info from periodic table.

g X → mol X → mol Y → g Y

2 CuO (s) + C(s) → 2 Cu(s) + CO2

We want to produce 35 mol Cu. • How many moles of copper (II) oxide do we

need?

• How many moles of carbon do we need?

2 CuO (s) + C(s) → 2 Cu(s) + CO2

We want to produce 500 g CO2.

• How many moles of copper (II) oxide do we need?

• How many moles of carbon do we need?

2 CuO (s) + C(s) → 2 Cu(s) + CO2

We want to produce 7,345 g Cu.• How many grams of carbon do we need?

• How many grams of CO2 will be produced in the process?

2 CuO (s) + C(s) → 2 Cu(s) + CO2

We want to produce 7,345 g Cu.• How many grams of CuO do we need?

9,194.3 g CuO

17

C.9 Percent Composition

Turn to pg. 167.If you had 1 mole of each of the minerals, how many copper atoms would you have in each mole?Which mole would be the heaviest?

Cu2S 159.17 g/mol

CuFeS2 183.54 g/mol

Cu2CO3(OH)2 221.126 g/mol

Which one has the most copper for every gram of the mineral?

18

C.9 Percent Composition

• Percent composition gives the percentage (by mass) of an element in a substance.

• If you are given a formula, use the molar mass.

19

Cu2S

CuFeS2

Cu2CO3(OH)2

20

Ex: A post-1982 penny with a mass of 2.5 g is composed of 2.4375 g zinc and 0.0625 g copper. What is the percent composition of each element?

97.5% zinc2.5% copper

21

Ex: Find the percent composition of each element in glucose, C6H12O6