1. 4S6
Welcome To my Chemistry Class~

2. Number of
particles
Number of Avogadro
Moles c onstant
Particles= Atoms, molecules, ions
Avogadro constant = 6.02 x 1023
(Mary No Car)
1. Number Of Particles = number of moles x Avogadro constant
2. Number Of Moles = number of particles ÷ Avogadro constant

3. RECALL BACK….
 1 mole of Carbon = 6.02 x 1023 atoms
 1 mole of H20 = 6.02 x 1023 molecules
 1 mole of Fe2+ = 6.02 x 1023 ions
 1 mole of O2 = 6.02 x 1023 molecules
= 2 x 6.02 x 1023 atoms

4. CALCULATE THE NUMBER OF ATOMS IN 3 MOL
OF COPPER ATOMS.
Cu
Number of Atoms
= Number of mole x Avogadro Constant
= 3 x 6.02 x 1023
= 1.806 x 1024 mol of copper atoms

5. CALCULATE THE NUMBER OF MOLECULE IN 0.5
MOL OF CO2
O
C
O
Number of molecule
= Number of mole x Avogadro Constant
= 0.5 x 6.02 x 1023
= 3.01 x 1022 mol of carbon dioxide

6. Calculate the number of Ions in 0.5 mol
of Pb2+
Pb2+
Number of ions
= Number of mole x Avogadro Constant
= 0.4 x 6.02 x 1023
= 2.408 x 1022 mol of Pb2+

7. CALCULATE THE NUMBER OF ATOMS IN 0.5 MOL
OF CO2
O
C
Number of atoms O
= Number of mole x Avogadro Constant
= 3 x 0.5 x 6.02 x 1023
= 9.03 x 1023 mol of carbon dioxide
atoms

8. EXAMPLE 2:
a. Calculate the number of moles of atoms in 1.204 x
1025 iron atoms.
b. Calculate the number of moles of ions in 6.02 x
1021 copper(II) ions, ____
c. Given 1.505 x 1024 oxygen gas, , calculate
i) the number of moles of oxygen molecules,
ii) the number of atoms of oxygen atoms
d. Given 2.408 x 1025 hydrogen atoms, calculate
i) the number of moles of hydrogen atoms.
ii) the number of moles of hydrogen molecules,

9. A.CALCULATE THE NUMBER OF MOLES OF
ATOMS IN 1.204 X 1025 IRON ATOMS.
Number of Moles
= Number of particles
Avogadro Constant
= 1.204 x 1025
6.02 x 1023
= 20 mol of iron atoms

10. B.CALCULATE THE NUMBER OF MOLES OF IONS IN
6.02 X 1021 COPPER(II) IONS, ____
Number of Moles
= Number of particles
Avogadro Constant
= 6.02 x 1021
6.02 x 1023
= 0.01 mol of copper(II) ions

11. C. GIVEN 1.505 X 1024 OXYGEN GAS, , CALCULATE
I) THE NUMBER OF MOLES OF OXYGEN MOLECULES,
Number of Moles
= Number of particles
Avogadro Constant
= 1.505 x 1024
6.02 x 1023
= 2.5 mol of Oxygen molecules

12. C. GIVEN 1.505 X 1024 OXYGEN GAS, , CALCULATE
II) THE NUMBER OF ATOMS OF OXYGEN ATOMS
2 x 1.505 x 1024
= 3.01 x 1024 oxygen atoms
O
O O
O O
O O
O
1 O2 molecule = 2 O atoms

13. D. GIVEN 2.408 X 1025 HYDROGEN ATOMS, CALCULATE
I) THE NUMBER OF MOLES OF HYDROGEN ATOMS.
II) THE NUMBER OF MOLES OF HYDROGEN MOLECULES,
i) Number of Moles
= Number of particles
Avogadro Constant
= 2.408 x 1025
6.02 x 1023
H
= 40 mol of hydrogen atoms H
ii) 40 mol of hydrogen atoms
÷2 H
= 40 H
= 20 mol of hydrogen molecules

14. NOTE:
 The gases which exist as diatomic molecules are:
O2 H2 N2 Cl2 Br2 I2
Cl
Cl
O
H
O H
I I

15. 3.3 THE MOLE AND THE MASS OF SUBSTANCES
A. The molar mass
 - is the mass of one mole of any substance.
 The molar mass of a substance = the mass of
1 mole
_______ of substance = the mass of
____________ particles.
 -the unit of molar mass is ________.
12
 1 mol of carbon-12 has a mass of exactly _____g.
12
 So, the molar mass of carbon-12 is __________.

16. THE MOLAR MASS OF ALL THE OTHER SUBSTANCES
ARE NUMERICALLY EQUAL TO THEIR RELATIVE
MASSES.
 Examples:
 The relative atomic mass of sodium = 23, so, the
23
molar mass of sodium = ____________
 The relative atomic mass of water, so, the molar
18
mass of water = ____________

17. Mass
Number of Relative
atomic
Moles Mass/ RMM
(Mario Miss Rainbow)

18. EXAMPLE 1:
 a. Calculate the mass of 2 mol of carbon atoms
 b. Calculate the mass of 5 mol of oxygen gas,
 c. calculate the mass 0.4 mol of magnesium oxide,
MgO.

19. CALCULATE THE MASS OF 2 MOL OF
CARBON ATOMS
The molar mass of carbon atoms = 12gmol-1
so, the mass of 2 mol of carbon atoms
= 2 mol x 12gmol-1
= 24g

20. CALCULATE THE MASS OF 5 MOL OF
OXYGEN GAS
the mass of 5 mol of oxygen gas
= 5 mol x 32gmol-1
= 160g

21. Calculate the mass 0.4 mol of magnesium oxide, MgO.
The molar mass of MgO = 24+16 = 40gmol-1
The mass of 0.4 mol of magnesium oxide
= 0.4 mol x 40gmol-1
= 16g

22. ANSWER
a) The molar mass of carbon atoms = 12gmol-1
so, the mass of 2 mol of carbon atoms
= 2 mol x 12gmol-1
= 24g
b) The molar mass of oxygen gas = 2(16) = 32gmol-1
so, the mass of 5 mol of carbon atoms
=5 mol x 32gmol-1
= 160g
c) The molar mass of MgO = 24+16 = 40gmol-1
so, the mass of 0.4 mol of MgO
= 0.4 mol x 40gmol-1
= 16g

23. EXAMPLE 2:
 a. How many moles of atoms are there in 18g of
carbon?
 b. How many moles of sodium chloride are there in
14.625g of sodium chloride, NaCl?
 c. Given 6.4g of oxygen gas, calculate
 i) the number of moles of oxygen gas.
 ii) the number of moles of oxygen atoms.

24. How many moles of atoms are there in 18g of carbon?
The molar mass of carbon atoms = 12gmol-1
The number of moles of carbon atoms = 18 g
12gmol-1
= 1.5mol

25. How many moles of sodium chloride are there in
14.625g of sodium chloride, NaCl?
The molar mass of sodium chloride, NaCl
= 23 + 35.5=58.5gmol-1
So, the number of moles of NaCl =14.635 g
58.5gmol-1
=0.25mol

26. O
Given 6.4g of oxygen gas, calculate
i) the number of moles of oxygen gas. O
The molar mass of Oxygen gas = 2(16) = 32gmol-1
So, the number of moles of oxygen gas = 6.4 g
32gmol-1
= 0.2mol

27. II) THE NUMBER OF MOLES OF OXYGEN ATOMS.
ii) The number of moles of oxygen atoms O
= 2 x 0.2 mol = 0.4 mol
O

28. ANSWER:
a) The molar mass of carbon atoms = 12gmol-1
The number of moles of carbon atoms = 18 g
12gmol-1
= 1.5mol
b) The molar mass of sodium chloride, NaCl = 23 + 35.5 = 58.5gmol-1
So, the number of moles of carbon atoms=14.635 g
58.5gmol-1
= 0.25mol
b) i) The molar mass of Oxygen gas = 2(16) = 32gmol-1
So, the number of moles of oxygen gas = 6.4 g
32gmol-1
= 0.2mol
ii) The number of moles of oxygen atoms
= 2 x 0.2 mol = 0.4 mol

29. EXAMPLE 3:
 a. Calculate the mass of 6.02x 1021 iron atoms.
 b. How many molecules of oxygen are there in 12.8
g of oxygen gas?

30. a. Calculate the mass of 6.02x 1021 iron
atoms. Fe
Number of moles
= 6.02 x 1021
6.02 x 1023
= 0.01 mol
The mass of 6.02x 1021 iron atoms
= 0.01mol x 56gmol-1
= 0.56g

31. How many molecules of oxygen are thereO
in 12.8 g of oxygen gas?
Number of moles O
= 12.8 g
32gmol-1
= 0.4 mol
Number of molecule of oxygen
= 0.4 x 6.02 x 1023
= 2.408 x 1023 molecules of oxygen

32. ANSWER:
a. 6.02 x 1021 iron atoms = 6.02 x 1021
6.02 x 1023
= 0.01 mol
0.01 mol of iron atoms = 0.01mol x 56gmol-1 = 0.56g
b) 12.8g of oxygen gas = 12.8 g
32gmol-1
= 0.4 mol
0.4mol of oxygen gas = 0.4 x 6.02 x 1023
= 2.408 x 1023 molecules of oxygen

33. PASS UP THURSDAY(28/2/2013)

34. Cl-
Zn2+
Cl-
1 ZnCl2 = 1 Zn2+ ion 2 Cl- ions