Unit 5 – Chemical Quantities & The

Mole

Molar mass is the mass of one moleof a substance.

Other names for molar mass include…*formula mass

*gram formula mass*molecular weight

Molar Mass

Molar Mass

• One _____________of any element will

have a mass in grams corresponding to

the value of its ____________________.

o1 mol carbon = __________ g/mol

o1 mol calcium = ___________ g/mol

o(its atomic mass from the periodic table

= 1 mole)

mole

atomic mass

12.011

40.078

Diatomic Elements never exist alone in

nature!!!

*Trick for remembering the 7 diatomics *

Molar Mass of Compounds

• One ________ of any

molecule/compound will have a

mass in grams corresponding to the

value of its molar mass (the sum of the masses of the elements that

compose it).

mol

http://app.discoveryeducation.com/search?Ntt=moles

Example: Water, H2O

Element Molar Mass # of Atoms Total

H

O2

1

1.008

15.999

X

X

2.016 g

15.999 g

18.015 g/mol

This is the mass of 1 mol of water!

Ex. Ca(NO3)2

Ca: 40.078 x 1 = 40.078

N: 14.007 x 2 = 28.014

O: 15.999 x 6 = 95.994

--------------

164.086 g/mole

Sample Problems

Potassium carbonate ___________K2CO3

# of K atoms: x =+

# of C atoms: x =+

# of O atoms: x =

___________________

39.098

12.011

15.999

2

1

3

78.196

12.011

47.997

138.204 g K2CO3

Sample Problems

Ammonium sulfate _____________(NH4)2SO4

# of N atoms: x =+

# of H atoms: x =+

# of S atoms: x =+

# of O atoms: x =

_________________________

14.007

1.008

32.066

2

8

1

28.014

8.064

32.066

132.140 g (NH4)2SO4

15.999 4 63.996

Practice

1. What is the atomic mass of sodium?

2. Calculate the molar mass of Al2(SO4)3

3. Calculate the molar mass of nitrogen

(hint: diatomic!?!?).

Mole HighwayNOTES: To convert between units, follow the highway. Notice, there is no shortcut from grams to liters or between any of the three units surrounding the mole.

This means you have to convert to molesbefore converting to another unit!

Draw the Mole Road Map!!

Molar mass:

• called gram atomic mass when single element is used.

• called gram formula unit when ionic compound is used.

• called gram molecular unit when molecular compound or

diatomic molecules used.

• Diatomic molecules are atoms that bond with themselves.

There are SEVEN of these that you need to remember: Br2 I2N2 Cl2 H2 O2 F2 (Remember this by the name “BRINClHOF”)

Determine the number of moles in….

• 25 g sodium

25 g 1 mol

22.990 g= 1.1 mol

Molar mass of Sodium =

Na = 1 x 22.990 = 22.990 g

Determine the number of moles in….

• 85 g H2SO4

85 g 1 mol

98.078 g= 0.87 mol

Mass in grams of H2SO4 =

H = 2 x 1.008 =

S = 1 x 32.066 =

O = 4 x 15.999 =

Add to get molar mass of 98.078 g

Determine the number of grams in….

• 2.5 moles of sodium

2.5 mol 22.990 g

I mol= 57 g

Molar mass of Sodium =

Na = 1 x 22.990 = 22.990 g

Determine the number of grams in….

• 0.50 moles of H2SO4

0.50 mol 98.078 g

I mol= 49 g

Mass in grams of H2SO4 =

H = 2 x 1.008 =

S = 1 x 32.066 =

O = 4 x 15.999 =

Add to get molar mass of 98.078 g

How many moles are there in 27 g of

ethanol (C2H5OH)?

27 g 1 mol

46.069 g= 0.59 mol

Mass of C2H5OH:

C = 2 x 12.011=

H = 6 x 1.008=

O = 1 x 15.999=

Add these all up for mass in grams = 46.069 g

Homework page 7

Show all work and units to receive full credit.

Representative Particles Moles

It’s a quantity, and it’s a BIG one.

• Avogadro’s Number = ______________

and is also called a _______.

• Like a “pair” or “dozen,” a “mole”

represents a set number of things; in

chemistry, those “things” are particles.

For example:

• 1 dozen = ______ items

• 3 dozen = ______ cookies

• .5 dozen = ______ doughnuts

6.02 x 1023

Mole

12

36

6

It’s a quantity, and it’s a BIG one.

So, a “dozen” is a counting unit

equal to __12__of any object.

Likewise, a “Mole” is a counting

unit equal to _____________ of an

object, even really small ones like

____________, ____________, or

_____________.

6.02 x 1023

atoms molecules

formula units

What’s so special about 6.02 x 1023?

• Why do scientists use that number?

oA conversion factor.

oAllows us to manipulate many small

particles, as if they were one whole

part.

o For elements on the periodic table, there is a 1

to 1 relationship between the mass of a single

atom (in amu) and the mass of 1 Mole of the

same species of atom (in grams).

o Remember, Mole is a quantity…6.02 x 1023

particles.

What’s so special about 6.02 x 1023?

Using the periodic table, we’ve learned that an Argon atom has a mass of 39.95 amu.

Unfortunately, manipulating a single atom of any element isn’t reasonable, so taking its individual mass isn’t possible.

However, we do have the Mole…

Atomic Number

(number of protons)

Atomic Mass

(average number of

protons and neutrons)

Ar

1 Atom of Argon 1 Mole of Argon

•So, a 39.95 g sample of

Argon contains 6.02 x 1023

atoms…that’s Avogadro’s

Number, the MOLE!

•It’s a 1 to 1 relationship

between a single atom in

amu and a Mole of atoms

in grams.

Representative Particles

• A representative particle

is the smallest unit of a

substance.

Types of Particles

• Monatomic elements = _______________

• Diatomic elements = _________________

• Ionic compounds = _________________

• Covalent compounds = ______________

• Ions = _________________

• Acids = _________________

atoms

molecules

formula units

molecules

atoms

molecules

Avogadro’s number, which is

________________, represents the

number of “chemical units” in

one mole of any substance. For

the monatomic elements, the

“chemical unit” is an __________.

1 mol of any chemical =

______________ particles.6.02 x 1023

atom

6.02 x 1023

Examples

• 1 mol CaCl2 =

• 1 mol Ca2+ =

• 1 mol HCl (aq) =

• 1 mol P2O5 =

• 1 mol Ca =

• 1 mol Cl2 =

6.02 x 1023 formula units

6.02 x 1023 atoms

6.02 x 1023 molecules

6.02 x 1023 molecules

6.02 x 1023 molecules

6.02 x 1023 atoms

1. How many moles are in 4.50 x 105

atoms of manganese?

4.50 1025 atoms 1 mol

6.02 1023 atoms

= 74.8 moles

Sample problems

2. How many atoms are found in

3.27 mol of magnesium?

3.27 mol 6.02 1023 atoms

1 mol

= 1.97 1024 atoms

Sample problems

3. Chalk is composed primarily of calcium

carbonate. How many particles are in

3.4 moles of calcium carbonate?

3.4 mol 6.02 1023 formula units

1 mol

= 2.0 1024 formula units

Sample problems

Moles of Chalk Lab

Homework page 10

Show all work and units to receive full credit.