1. Mole Recap

2. What is a mole? A mole is a very large number of atoms or molecules
6.02 x 10 23

3. What we know....
ma= relative atomic mass - sometimes also written as Ar
n = number of moles (mol)
M = molar mass (g/mol)
NA = Avogadros constant
N = number of molecules or atoms

4. What was Avogadro thinking....
Given the relative atomic mass, ma, a carbon atom must be 12 times heavier than a hydrogen atom etc.
From the periodic table
Therefore, if he took 12 times more mass of carbon than hygrogen (12g vs. 1 g ) he should have the same amount of atoms.
16g of oxygen, 12g of carbon, 1g of hydrogen should all have the same amount of atoms.
Then he counted this amount of atoms x and named it the Avogadro constant NA or the mole.

5. Formula – to convert number of atoms to moles
n (mol) = N NA n = moles N = number of aoms or molecules present NA = Avogadros constant = 6.02 x 10 23

6. Worked example
Calculate the amount in moles of carbn dioxide in a sample of 1.50 x molecules.
n = N /NA
n (CO2) = 1.5 x / 6.02 x 1023
N (CO2) = mol

7. Try these now Calculate the amount of molecules of H2O in 0.236 moles.
Calculate the number of carbon atoms contained in 1.50 mol of glucose C6H12O6

8. Answer
N = n x NA = x NA = x 1023
1 mole of glucose conatines 6 atoms of carbon, 12 atoms of H and 6 atoms of O
1 mole of glucose contains 6 moles of C
1.5 mole of glucose contains 9 moles of C
N = 9 x NA
N = 5.42 x1024 C atoms

9. Whats the difference between molar mass and relative atomic mass?
Nothing really  - just the units
To work out the molar mass for a molecule we add the the molar masses of each element in the molecule.
M (H2O) = 2 x M(H) + M(O)
= 2 x 1 𝑔 𝑚𝑜𝑙 𝑔 𝑚𝑜𝑙
= 18 𝑔 𝑚𝑜𝑙
Try:
CO2
CH4
NaCl

10. Now we can do qualitative chemistry...
The mass, molar mass and number of moles are related.
n (mol) = m (g)
Mr (g/mol)
n = number of moles
m = mass
Mr = molar mass

11. Worked example
Calculate the amount in mol in 8.80g of carbon dioxide CO2
n(CO2) = m / Mr = 8.80g / g/mol = mol
Mr (CO2) = (16.00) = g/mol

12. Try these now Calculate the amount (in mol) of the following masses.
8.09 g of Aluminium, Al
9.8g of sulfuric acid H2SO4

13. Answers n (Al)= m/Mr n (Al) = 8.09 g / 26.98 g/mol = 0.30 mol
n(H2SO4) =. m/Mr. = 9.8 / = 0.10 mol
Mr (H2SO4) = 2x x16.00 = 98.03

14. Molar concentrations
Molar concentrations tell us how many moles of a substance are dissolved in 1 liter of a solution
The symbol for the molar concentration is c, it‘s unit 𝑚𝑜𝑙 𝑙
Since the volume of a dilute solution barely changes when the substance is dissolved, we can calculate the concentration of a solution we make in advance

15. Concentration calculation
c = n / v c = concentration (mol/ l) n = number of moles (mol) v = volume (l)

16. Molar concentration The molar mass Mr of NaOH is 40 𝑔 𝑚𝑜𝑙
If 40 g of NaOH are dissolved in 1 litre of solution, the concentration of the resulting solution is c = 1 𝑚𝑜𝑙 𝑙
n = m/Mr. = 40g / 40 g/mol. = 1 mol
c = n/v = 1/1 = 1 mol/l

17. Try these
Determine the concentration of 1 litre of solution containing 117 g of sodium chloride (NaCl)
Determine the mass of sodium hydroxide (NaOH) in 500 ml of a solution with c = 4 𝑚𝑜𝑙 𝑙

18. The grand finale: Mole Traffic lights
You have to decide, whether the statements are true or false
False Sit down
Don‘t know Stand up True Stand up with hand in the air

19. The grand finale: Mole Traffic lights
The mole is a unit
The mole is a mass
One mole of water (H2O) and one mole of glucose (C6H12O6) have the same mass
One mole of H2 contains the same number of molecules as one mole of CO2
One mole of H2 contains the same number of atoms as one mole of CO2
There are more atoms in 12 g of carbon than in 12 g of copper

20. The grand finale: Mole Traffic lights
A mole is a molecule
The mole is a number
One mole of a substance contains Avogadro‘s number of atoms or molecules
One mole of a substance contains 6,02 x 1023 atoms or molecules
The amount of a substance is measured in kilograms
The amount of substance is a volume
I understand what a mole is