Starter S-89

1. List the elements and how many there are of each in Iron (III) oxide.

2. Multiply the number of each element by the average atomic mass of each.

3. Add these numbers together, this is called the molar mass.

Starter S-90

1. What is the molar mass of H2S?

2. How many moles of H2S would be found in 100 g?

3. How many formula units (particles) of H2S would be in 100g?

Remember the lab from Tuesday

Chemical Quantities

Chapter 10

10.1 The Mole: A Measurement of Matter

Chapter 10

Quantitative – yield a number value

Most common methods

count

mass

volume

10.1 The Mole

Words often mean a quantity

pair – 2

dozen – 12

mole?

10.1 The Mole

10.1 The Mole

Mole – means a specific number of particles

This is called Avogadro’s Number

The unit is used for

atoms

molecules (covalent compounds)

formula units (ionic compounds)

2310022.6 x

10.1 The Mole

10.1 The MoleTo convert numbers of particles to moles we need

an equality

This could also be

Or

Depending on what type of particle you are trying to convert

atomsxmol 2310022.61

10.1 The Mole

moleculesxmol 2310022.61

unitsformulaxmol .10022.61 23

10.1 The MoleThe rest is just the conversion we have always done

remember – the unit you have goes on the bottom of the fraction

-the unit you are converting to goes on the top

So to convert 2500 atom of C to moles

10.1 The Mole

atomsCx

molCatomC

2310022.6

12500

molCx 21102.4

10.1 The MoleConverting from moles to partciles follows the same

process

How many molecules of Carbon Dioxide are in 1.55 mol?

10.1 The Mole

2

223

2 1

10022.655.1

molCO

OmoleculesCxmolCO

2231033.9 OmoleculesCx

10.1 The MoleConvert the following quantities to moles

1. 9,487,212 formula units of AgNO3

2. 5.78x1023 atoms of Nitrogen

3. 4.1x1024 molecules of Carbon Monoxide

10.1 The Mole

31710575.1 molAgNOx

molN960.0

molCO8.6

10.1 The MoleConvert the following to the correct type of particle

1. 95 moles of CCl4

2. 7.211x10-3 moles of CuCO3

3. 0.08 moles of Helium

10.1 The Mole

425107.5 ClmoleculesCx

321 .10342.4 unitsCuCOformulax

atomsHex 22105

10.1 The MoleBy definition, the atomic mass of an element in

grams is the mass of one mole of the element.

This is called the molar mass

10.1 The Mole

10.1 The MoleFor a compound we must calculate the molar mass

1. Write down what type of atoms, and how many of each are present

C 1

H 4

2. Multiply by the molar mass of each element

10.1 The Mole

CH4

10.1 The MoleFor a compound we must calculate the molar mass

1. Write down what type of atoms, and how many of each are present

C 1 x 12.0107g =

H 4 x 1.00794g =

2. Multiply by the molar mass of each element

10.1 The Mole

CH4

10.1 The MoleFor a compound we must calculate the molar mass

1. Write down what type of atoms, and how many of each are present

C 1 x 12.0107g = 12.0107g

H 4 x 1.00794g = 4.03176g

2. Multiply by the molar mass of each element

3. Add to get a total

10.1 The Mole

CH4

10.1 The MoleFor a compound we must calculate the molar mass

1. Write down what type of atoms, and how many of each are present

C 1 x 12.0107g = 12.0107g unit

H 4 x 1.00794g = 4.03176g

2. Multiply by the molar mass of each element

3. Add to get a total 16.0425g CH4

10.1 The Mole

CH4

Starter S-92

1. What is the molar mass of CO?

2. How many moles of CO would

be found in 0.56 g?

3. How many molecules of

CO would be found in

3.51 moles?

10.2 Mole-Mass and Mole-Volume

Chapter 10

10.1 The Mole

10.2 Mole-Mass and Mole-Volume

We don’t convert from particles to moles nearly as often as we do from moles to grams.

The reason is that we usually measure the amount of a substance on the balance

We need to know numbers of

particles so that we can

compare ratios of atom or

compounds

10.1 The Mole

10.2 Mole-Mass and Mole-Volume

This is just another conversion problem

The equality is

Again, the quantity you have goes on the bottom, the quantity you want goes on top

So if you have 9.5g of Carbon

Value Molar Mass = 1 mole

molCgC

molCgC 79.0

0107.12

15.9

10.1 The Mole

3AgNO

10.2 Mole-Mass and Mole-Volume

If you have 2.2 moles of Silver Nitrate convert to mass

First we need to know the formula of Silver Nitrate

Then the molar mass

And finally we can convert

g8731.169

33

33 370

1

8731.1692.2 gAgNO

molAgNO

gAgNOmolAgNO

Try the following example: How many moles is 8.2g of Copper (II) Chloride

Formula

Molar mass

Moles

10.1 The Mole

2CuCl

10.2 Mole-Mass and Mole-Volume

g451.134

22

22 061.0

451.134

12.8 molCuCl

gCuCl

molCuClgCuCl

And another one: How many grams is 2.4 mol of Iron (III) Sulfate

Formula

Molar mass

Moles

10.1 The Mole

342 SOFe

10.2 Mole-Mass and Mole-Volume

g881.399

342

342

342342 960

1

881.3994.2 SOgFe

SOmolFe

SOgFeSOmolFe

In 1811, Amedeo Avogadro proposed

Avagador’s Hypothesis – equal volumes of gases at the same temperature and pressure contain equal numbers of particles

10.1 The Mole

10.2 Mole-Mass and Mole-Volume

Standard Temperature and Pressure (STP)

T – 0oC or 273K

P – 101.3 kPa, or 1 atm

At STP the volume of one mole is 22.4L

So the equality for conversion is

10.1 The Mole

10.2 Mole-Mass and Mole-Volume

Lmol 4.221

To do these problems, the identity of the gas doesn’t really matter.

If we have 15 L of Chlorine gas

The number of moles would be

10.1 The Mole

2Cl

10.2 Mole-Mass and Mole-Volume

22

22 67.0

4.22

115 molCl

LCl

molClLCl

If instead we calculate for a more complicated gas such as propane

And we also have 15 L of propane gas

The number of moles would be

10.1 The Mole

83HC

10.2 Mole-Mass and Mole-Volume

8383

8383 67.0

4.22

115 HmolC

HLC

HmolCHLC

Starter S-96

1. What is the molar mass of Pb(SO4)2?

2. How many moles of Pb(SO4)2 would be found in 250 g?

3. How many moles of H2 gas are found in 250 L?

10.3 Percent Composition and Chemical Formulas

Chapter 10

The relative amounts of the elements in a compound is called the percent composition

The percent by mass of an

element is the number of

grams of the element

divided by the mass in

grams of the compound multiplied by 100%

10.1 The Mole

10.3 Percent Composition

.% 100%

.

mass elementmass x

mass compound

Calculating the mass percent from a formula

1. Formula

2. Calculate the total

mass of each element

3. Calculate the total

mass of

the compound

4. Calculate the

percent by

mass for

each element

10.1 The Mole

1 12.0107 12.0107

4 1.00794 4.03176

C x g g

H x g

4CH

10.3 Percent Composition

4 12.0107 4.03176 16.0425CH g

12.0107100% 74.8680%

16.0425

4.03176100% 25.1317%

16.0425

C x

H x

Calculate the mass percent

1. Formula

2. Mass of each element

3. Total mass

4. Mass Percent

10.1 The Mole

1 12.0107 12.0107

4 1.00794 4.03176

1 15.9994 15.9994

C x g g

H x g

O x g

3CH OH

10.3 Percent Composition

3 12.0107 4.03176 15.9994 32.0419CH OH g

12.0107100% 37.4844%

32.0419

4.03176100% 12.5828%

32.0419

15.9994100% 49.9327%

32.0419

C x

H x

O x

Starter S-95

What is the percent by mass of the all the elements in Cu(NO3)2.

Empirical Formula – smallest whole number ratio of the elements in a

compound

The empirical formula

can be calculated

from the percent

composition

10.1 The Mole

10.3 Percent Composition

Compound Empirical Formula

H2O H2O

CH3COOH CH2O

CH2O CH2O

C6H12O6 CH2O

S8 S

To calculate the empirical formula

1. List the elements and their

percent compositions

2. Convert the percent

compositions to moles

3. Calculate the mole ratio (divide

by the smallest number of moles)

4. Smallest Whole Number ratio

5. Write the Formula

10.1 The Mole

25.9%

74.1%

N

O

10.3 Percent Composition

125.9 1.85

14.0

174.1 4.63

16.0

molNN gN molN

gN

molOO gO molO

gO

1.851.00

1.85

4.632.50

1.85

molN

mol

molO

mol

2

5

N

O

2 5N O

To calculate the empirical formula

1. Elements

2. Convert to Moles

3. Mole ratio

4. Whole Number ratio

5. Write the Formula

10.1 The Mole

67.6%

10.8%

21.6%

Hg

S

O

10.3 Percent Composition

167.6 0.337

200.59

110.8 0.337

32.06

121.6 1.35

16.0

molHgHg gHg molHg

gNg

molSS gS molS

gS

molOO gO molO

gO

0.3371.00

0.337

0.3371.00

0.337

1.354.01

0.337

molHg

mol

molS

mol

molO

mol

1

1

4

Hg

S

O

4HgSO

Starter S-97

What is the empirical formula if

Lead is 59.7%

Hydrogen is 2.9%

Arsenic is 21.6%

Oxygen is 18.4%

The molecular formula can be calculated from the empirical formula and the molar mass

10.1 The Mole10.3 Percent Composition

Comparison of Empirical and Molecular Formulas

Formula Classification Molar Mass

CH Empirical 13

C2H2 Molecular 26 (2x13)

C6H6 Molecular 78 (6x13)

CH2O Empirical 30

C2H4O2 Molecular 60 (2x30)

C6H12O6 Molecular 180 (6x30)

Steps in calculations (if mass=60.0g)

1. Determine the empirical formula

2. Calculate the mass

of the empirical formula

3. Divide the actual molar mass by

this number

4. Multiply the empirical formula

10.1 The Mole10.3 Percent Composition

4CH N1 12.0 12.0

4 1.01 4.04

1 14.0 14.0

C x gC

H x gH

N x gN

4 30.0CH N g

60.02.00

30.0

g

g

2 8 2C H N

Starter S-99

What is the empirical formula if

Silver – 63.5%

Nitrogen – 8.2 %

Oxygen – 28.2%

If the formula mass is 170g, what is the formula of this compound?

Practice Problem 1

A. How many moles of AgNO3 are found in 125 g?

B. How many grams of AgNO3 are found in 2.99 moles?

Practice Problem 2

A. How many molecules are found in 19.5 moles of CH2O?

B. How many grams of CH2O are found in 1.8x1024 molecules?

Practice Problem 3

A. What is the empirical formula of the following compound

Na-43.4%

C – 11.3%

O – 45.3%

Practice Problem 4

A. What is the empirical formula

C – 3.2g

H – 0.53g

O – 4.3 g

B. If the molar mass is 330, what is the molecular formula?

Starter S-102

Test Day

Great and Glorious Test Day

Yahoo

Yipee

Yah

Starter S-105

What is the empirical formula if

Carbon – 49.5%

Hydrogen – 5.2%

Nitrogen – 28.9%

Oxygen – 16.5%

What if the molecular formula, if the molar mass is 194g?