The MoleThe Mole

Molar Mass0 Also called atomic mass, formula mass, molecular mass0 Unit = g/mol

0Calculating Molar Mass0 Use the average atomic mass from the periodic table0 For atoms = atomic mass

Ex. C = 12.011 g/mol Fe = 55.847 g/mol

0 For compounds = sum of the atomic masses of the atoms that are in the formula

0 EX: CaI2 = 40.078 g/mol + 2 (126.904) g/mol = 293.886 g/mol0 EX: (NH4)3PO4 = 3(14.007) + 12(1.0079) + 30.974 + 4(15.999) =

149.086 g/mol

The Mole0 How do you measure how much you have?

0 Counting (impractical – too many particles)0 Weighing 0 Volume

0 Particles cannot be counted directly, but we need to know how many particles are there.0 In chemistry we use the mole to figure out how many particles there

are when we weigh something or measure the volume of something.

0Mole = the SI unit for how much of a substance or amount0 The mole is a unit similar to dozen- just many more than 120 It tells you how many you have.

The Mole

1 dozen =

1 gross =

1 ream =

1 mole =

12

144

500

6.02 x 1023

There are There are exactlyexactly 12 grams of carbon-12 12 grams of carbon-12 in one mole of carbon-12.in one mole of carbon-12.

0Particles moles or moles particles• Use Avogadro’s Number = • 1 mole = 6.02 X1023 particles

(atoms, molecules, formula units) *FOR ANY SUBSTANCE

0Grams moles or moles grams• Use the molar mass from the periodic table.

0Liter moles or moles liter• For Gases at STP (standard temperature and pressure) • 1 mole = 22.4 L

Avogadro’s NumberAvogadro’s Number6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855).

Amadeo Avogadro

I didn’t discover it. Its just named after me!

I didn’t discover it. Its just named after me!

Calculating Formula MassCalculate the formula mass of carbon dioxide, Calculate the formula mass of carbon dioxide, COCO22..

12.01 g + 2(16.00 g) =12.01 g + 2(16.00 g) = 44.01 g44.01 g

One mole of CO2 (6.02 x 1023 molecules) has a mass of 44.01 grams

Avogadro’s Number0602,214,000,000,000,000,000,000 0Avogadro’s # of sheets of paper stacked one sheet

on top of another would reach beyond our solar system.

0Avogadro’s # of basketballs could create a new planet the size of Earth.

0Avogadro’s # of grains of rice would cover the land masses of the Earth to a depth to 75 meters.

0Avogadro’s # of pennies. You decided to give away $1 million dollars a day to every person on Earth , it would take more than 3000 years to distribute all of your money

Mole Relationships

Mole Mole

Atomsor molecules

Atomsor molecules

Liters Liters

Grams Grams

6.02 x

6.02 x 1010 2323

6.02 x

6.02 x 1010 2323

Ato

mic

Ato

mic

Mas

sM

ass

Ato

mic

Ato

mic

Mas

sM

ass

22. 4

L

22. 4

L

22. 4

L

22. 4

L

22.4L

Molar MassAvogadro’s Number

22.4 L/mol

ParticlesAtoms

Moleculesf.u.

Mole Mass (g)

Volume (L)

Particles

atoms, molecules

, or formula

units

Mass

Volume (Gas at STP)

Molar Mass

22.4

Avogadro’s Number

Mole Conversions

Calculations with Moles:Converting moles to grams

How many grams of lithium are in 3.50 moles of lithium?

3.50 mol Li= g Li

1 mol Li

6.94 g Li 24.324.3

Calculations with Moles:Converting grams to moles

How many moles of lithium are in 18.2 grams of lithium?

18.2 g Li= mol Li

6.94 g Li

1 mol Li2.622.62

Calculations with Moles:Using Avogadro’s Number

How many atoms of lithium are in 3.50 moles of lithium?

3.50 mol = atoms

1 mol

6.02 x 1023 atoms2.07 x 102.07 x 102424

Calculations with Moles:Using Avogadro’s Number

How many atoms of lithium are in 18.2 g of lithium?

18.2 g Li

= atoms Li

1 mol Li 6.022 x 1023 atoms Li

1.58 x 1024

6.94 g Li 1 mol Li

(18.2)(6.022 x 1023)/6.94

0 Ex. How many moles are in 8.04*1024 atoms Fe?

0? g = 8 mol Al2(SO4)3

Calculations with Moles:Using Standard Molar Volume

How many moles of hydrogen are in 100 L of hydrogen at STP?

100 L = mol

22.4 L

1 mol4.644.64

Calculations with Moles:Using Standard Molar Volume

How many liters are occupied by 3 moles of oxygen gas at STP?

3 mol = L

1 mol

22.4 L67.267.2

0 How many atoms are in 20.04 g Sn?

0How many liters are equal to 8 moles of CO2?

0 How many moles are equal to 2.4 L of O2?

0 How many grams of O2 are in 2.4 L O2?

Atom & Mole Ratios*Within a formula, subscripts can be considered

as the:0 # of atoms within molecules of the compound 0 the # of moles of that element within moles of the

compound. (Since avogadro’s # cancels out)

Example: H2O

Example: Ba3(PO4)2

Using Chemical Formulas:

A raindrop contains about 0.050g of H2O.

0 How many molecules of water?

0 How many atoms of O within the water?

0 How many atoms of H?

% Composition0 Percent Composition = The % by mass of each element in a

compound. 0 Mass of part X 100 = % composition Total Mass

Example: Find the % composition of Al2(SO4)3

*If you had 25.0 grams of this substance, How much would be Al?

Ex: Na2CO310H2O . Find the % of water in this hydrate.

EX: Find the % composition of a compound containing tin and chlorine if 18.35 g of the compound contains 5.74 g of tin.

Molecular/Empirical Formula

0 Empirical Formula = smallest whole number ratio of moles of the elements in a compound

0 Molecular Formula = actual number and kinds of atoms present in a compound

0 Ex. Molec Formula = N10O5 Emp Formula = N2O

Calculating Empirical Formula An empirical formula is a ratio of moles of each atom

in a compound. 1. Must have the moles of each atom.

*If you are given %, assume that you have 100 grams of the substance. Since % is out of 100, the % of each atom will equal grams of each atom. Convert grams to moles.

2. To find the lowest whole number ratio (mole ratio). Divide each # of moles by the smallest # of moles.

3. If a # in the ratio is .5 (.4 - .6), double everything.4. Apply ratio to atoms given as subscripts.

Ex. 25.9 g N & 74.1 g O

25.9 g N & 74.1 g O

Calculating Molecular Formula 1. Calculate the empirical formula mass (efm)2. Divide a given molar mass (molecular mass) by efm

0 Gives you the number of emp. form. in your molecular formula

3. Multiply the emp. form. by that #Ex. EF = CH4N Molar Mass = 60 g/mol

EX: EF = NO2 Molar Mass = 138 g/mol

Ex. 27.59 %C, 1.15 %H, 16.09 %N, 55.17 %OMolar mass = 261.1 g/mol. Find molecular formula