THE MOLE... a unit of counting. Review How many oxygen atoms in the following? CaCO 3 Al 2 (SO 4 ) 3 How many ions in the following? CaCl 2 NaOH Al 2.

THE MOLE... a unit of counting

Review

• How many oxygen atoms in the following?CaCO3

Al2(SO4)3

•How many ions in the following?CaCl2NaOHAl2(SO4)3

3 atoms of oxygen x 6.022 x 10 23

12 atoms of oxygen x 6.022 x 10 23

3 total ions x 6.022 x 10 23

2 total ions x 6.022 x 10 23

5 total ions x 6.022 x 10 23

Finding Number of Atoms or Molecules

How many atoms of copper are there in 2.0 moles?

N = nNA

Given:

n Cu = 2.0 mol

NA = 6.02 X 1023

N = nNA

= 2.0 mol X 6.02 X 1023 atoms

1 mol

= 1.2 X1024 atoms of copper

• Do you know how to measure out 3 moles of sugar or salt or water?–The mole is a counting unit, so we would have to count out 6.02x1023 particles of each substance. (no thank you)

• There are 2 ways we can use to measure out a number of moles of a substance.–Measure it in grams (a mass)–Or measure it in liters (a volume)

• Do you know how to measure out 3 moles of sugar or salt or water?–The mole is a counting unit, so we would have to count out 6.02x1023 particles of each substance. (no thank you)

• There are 2 ways we can use to measure out a number of moles of a substance.–Measure it in grams (a mass)–Or measure it in liters (a volume)

How we measure moles…

Using a formula

• N = Number of particles , ions, atoms, molecules or formula units

• NA = Avogadros number

• n = number of moles

• n = N / NA

• N = n x NA

• Note on calculator x 10 is the same as EXP or EE. DO NOT use them both

• On calculator use 6.022 EXP 23

N

NA n

Mole Calculations

MM

m

n

MM = m/n

n = m/MM

m = MMn

Factor Label!

Let the units guide you

N = nNA

n = N/NA

Determining Molar Mass

The mass of one mole is called “molar mass”

E.g. 1 mol Li = 6.94 g Li This is expressed as 6.94 g/mol Symbol MM

What is the molar mass of CO2?

Recall: Add the individual molar masses

MM(NH4)3PO4 = 3(N + 4H) + P + 4O

= 3N + 12H + P + 4O = 3(14.01) + 12(1.01) + 30.97 +

4(16.00) = 149.12 g/mol

The same as: Gram Molecular Mass (for

molecules) Gram Formula Mass (ionic compounds) Gram Atomic Mass (for elements)

molar mass is just a much broader term than these other specific masses

Converting Mass to Moles

Example: How many moles of calcium carbonate are there in 1.5 kg?

MM = m/n

n = m/M

m = Mn

Given:

m CaCO3 = 1500 g

MM = 40.08 + 12.01 + (3 X 16.00)

= 100.09 g/mol

n = m/MM

= 1500 g 100.09 g/mol

= 15 mol

n = 1500 g X 1 mol

100.09 g

= 15 mol

Converting Moles to Mass

Example: What is the mass in grams of 0.346 mol of sodium sulfate?

MM = m/n

n = m/M

m = Mn

Given:

n Na2SO4 = 0.346 mol

MM = (2 X 22.99) + 32.06 + (4 X 16.00)

= 142.04 g/mol

m = MMn

= 142.04 g X 0.346 mol

1 mol

= 49.1 g

Try These:

How much would 2.34 moles of carbon weigh?

How many moles of magnesium is 24.31 g of Mg?

28.1 grams C

1.000 mol Mg

How many sugar (sucrose, C12H22O11) molecules are there in a 1.00 kg bag?

Given:

m = 1.00 X 103 g

MM = (12 X 12.01) + (22 X 1.01) + (11 X 16.00)

= 342.34 g/mol

n = 1.00 X 103 g X 1 mol

342.34 g

= 2.921 mol

N = nNA

= 2.921 mol X 6.02 X 1023 molecules

1 mol

= 1.76 X1024 molecules of sugar

How many carbon atoms are there in a 1.00 kg bag of sugar (sucrose, C12H22O11) ?

N = 1.76 X 1024 molecules of sugar X 12 carbon atoms

1 molecule sugar

= 2.11 X 1025 carbon atoms

Moles

(mol)

Mass

(g)

# of molecules/atoms/ions

Volume (L) at STP

(0˚C, 101.3 kpa)

Concentration (mol/L)

6.02

X 1

023

g/m

ol

22.4

Vol

Learning check

1.How many atoms of Cu are present in 35.4 g of Cu?

2.How many atoms of K are present in 78.4 g of K?

3.What is the mass of 1.20 x 1024 molecules of glucose (C6H12O6)?

= 3.35 X 1023 atoms Cu

= 1.21 X 1024 atoms K

= 359 g

Learning Check!

How many atoms of O are present in 78.1 g of oxygen?

78.1 g O2 1 mol O2 6.02 X 1023 molecules O2 2 atoms O 32.0 g O2 1 mol O2 1 molecule O2

Measuring volume

MOLAR VOLUME, Vm

Volume occupied by 1 mole of any gas

22.4 L at STP (standard temperature and pressure) at 0°C and 1 atmosphere/ 103kPa (kilopascals)

24.8 L at SATPStandard Ambient Temperature and Pressure

( 20oC and 1 atmosphere )

Particles to moles or moles to particles

Mass to moles or moles to mass

Volume to moles and moles to volume

V = n x Vm

HOMEWORK

• Finish Grams-Mole Worksheet

• Mole Worksheet – Due Tuesday, April 9th