1. And Dimensional Analysis
Mole Questions
And Dimensional Analysis

2. OUTCOME QUESTION(S): Vocabulary & Concepts Avogadro’s number
C MOLAR CALCULATIONS
Understand the importance of the concept of the mole
and calculate the molar mass of various substances.
Interpret a balanced equation in terms of moles, mass,
and volumes of gases. Include: molar volume
Solve problems requiring interconversions between moles,
mass, volume, and number of particles.
Include: density
Vocabulary & Concepts 
Avogadro’s number

3. Just like a “dozen” means 12...
To make life easy, in chemistry we count particles by large groups called moles (n).
One mole is 6.02 x 1023 particles
Just like a “dozen” means 12...
This weird amount was chosen as it is exactly how many atoms of carbon needed to weigh grams
6.02 x 1023 particles (or 1 mole) of a substance will have a mass in grams equalling its formula mass.

4. The mass of 1 mole of anything is the molar mass - (g/mol)
Mass of 1 atom of K = amu
Mass of 1 mole of K atoms = g/mol
So this number represents two things – the mass of a single atom and the mass of a mole of atoms
The molecular mass of water (H2O) is 18.0 amu
1 mole of H2O = 2 H + 1 O
= 2(1.0) + 1(16.0)
So...the molar mass of water is 18.0 g/mol

5. What is the molar mass of calcium nitrate? Ca(NO3)2
Breakdown the compound:
1 Ca(NO3)2 particle = 1 Ca atom + 2 N atoms + 6 O atoms
1 Ca(NO3)2 mole = 1Ca mole + 2 N moles + 6 O moles
= (40.0) + 2(14.0) + 6(16.0)
So the molar mass of Ca(NO3)2 is g/mol

6. Mole is abbreviated mol or n
What is the molar mass of ammonium dichromate?
(NH4)2Cr2O7
Breakdown the compound:
1 (NH4)2Cr2O7 mole = 2 N mol+ 8 H mol + 2 Cr mol + 7 O mol
Mole is abbreviated mol or n
= 2(14.0) + 8(1.0) + 2(52.0) + 7(16.0)
So the molar mass of (NH4)2Cr2O7 is g/mol

7. Find the molar masses of these compounds:
You will need to write the formula in some cases.
Cu3(PO4)2
copper(II) phosphate
3Cu + 2P + 8O
381 g/mol
magnesium hydroxide
Mg(OH)2
Mg + 2O +2H
58 g/mol
dinitrogen trioxide
N2O3
2N + 3O
76 g/mol

8. We call this Avogadro’s Number (NA)
One mole is 6.02 x 1023 particles
We call this Avogadro’s Number (NA)
6.02 x particles
1 mole
6.02 x particles
1 mole or
The term "particle" refers to the known value: atoms, molecules, ions, etc.
6.02 x pencils is 1 mole of pencils
6.02 x carbon atoms is 1 mole…
6.02 x water molecules is 1 mole…

9. Rules for Dimensional Analysis
Start with what you know
Identify (or create) the conversion factor
Put units you want to cancel on bottom
Put units you need on the top
Multiply across top, divide across bottom
Dimensional Analysis is a way to convert units:
(make the value the same but in different units)
Some people simplify this notation with added bars – called “factor label line”
How many pizzas would 250 pieces of pepperoni make?
1 pizza
250 pepperoni
= 13.2 Pizzas
19 pepperoni

10. String multiple conversion factors together…
How many eggs in 25.0 dozen?
12 eggs
25.0 dozen
= 300 eggs
1 dozen
How many centimetres in 150 km?
String multiple conversion factors together…
150 km
1000 m
100 cm
= 1.5 x 107 cm
1 km
1 m

11. 1 mol 1 mol How many atoms in 25.0 moles of copper?
atoms are the “particle”
25.0 Cu mol
6.02 x 1023 particles
= 1.51 x 1025 Cu atoms
1 mol
How many molecules of water in 1.50 x 10–5 mol?
molecules are the “particle”
1.50 x 10-5
H2O mol
6.02 x 1023 particles
= 9.03 x H2O
molecules
1 mol

12. atoms are the “particle”
How many moles is 5 atoms of zinc?
atoms are the “particle”
5 Zn atoms
1 mol
= 8.31 x Zn mol
6.02 x 1023 particles
Note: all conversion factors can be flipped “upside down” depending on the need
6.02 x particles
1 mole
6.02 x particles
1 mole or
So 5 atoms of Zinc is the same as 8.31 x moles

13. Now lets add the molar mass to our dimensional analysis work…
What is the mass of 1.20 x 10–5 moles of carbon tetrachloride, CCl4?
Now lets add the molar mass to our dimensional analysis work…
CCl4 = 1 C + 4 Cl
= 1(12.0) + 4(35.5)
= g/mol
154.0 g
1 mol
154.0 g
1 mol
What you know
Add conversion factor
Units to cancel on bottom
Units in need on the top
Multiply top, divide bottom or
1.20 x 10-5 mol CCl4
1 mol
154.0 g
= 1.85 x 10-3 g

14. The mole allows the conversion between mass and number of particles

15. 1 mol = 0.556 mol of H2O 18 g = 3.34 x 1023 H2O molecules 1 mol
How many molecules of water in a 10.0 g sample?
H2O = 18.0 g/mol
Whenever the question involves mass (g) find the molar mass
10.0 g H2O
18 g
1 mol
= mol of H2O
0.556 mol
1 mol
6.02 x 1023 particles
= 3.34 x 1023 H2O molecules
This will take two steps…

16. Put the two equations together!
10.0 g H2O
1 mol
6.02 x 1023 particles
= 3.34 x 1023
molecules of H2O
18 g
1 mol
There are 3.34 x 1023 molecules in 10.0 g of water.
String multiple conversion factors together… to solve in one step!

17. This will take two steps…
How many particles of sodium chloride in 25.0 g?
NaCl = 58.5 g/mol
Need the molar mass…
1 mol
25.0 g NaCl
6.02 x 1023 particles
= 2.57 x 1023
particles of NaCl
58.5 g
1 mol
There are 2.57 x 1023 particles of NaCl in 25.0 g.
This will take two steps…

18. 1 mol 30 g 1 mol = 3.61 x 1023 atoms in total 1 particle
How many total atoms in 6.0 g of lithium oxide?
Li2O = 30 g/mol
Here our “particle” is NOT an atom; but, a compound
How does this change things?
1 mol
6.0 g Li2O
6.02 x 1023 particles
3 atoms
30 g
1 mol
1 particle
? atoms
1 particle
= 3.61 x 1023
atoms in total
We need to create a conversion factor!

19. CAN YOU / HAVE YOU? Vocabulary & Concepts Avogadro’s number
C MOLAR CALCULATIONS
Understand the importance of the concept of the mole
and calculate the molar mass of various substances.
Interpret a balanced equation in terms of moles, mass,
and volumes of gases. Include: molar volume
Solve problems requiring interconversions between moles,
mass, volume, and number of particles.
Include: density
Vocabulary & Concepts 
Avogadro’s number