Gram atomic mass
The mass, in grams, of 1 mole of an atom is equal to its
Use the periodic table to find out
1 mol of Carbon is 12.0g
1 mol of Nickel is 58.7g
Gram Molecular Mass and
Gram Formula Mass
= Molecular Mass
Gram molar mass. The mass of one mole of a molecule is
equal to the sum of the mass of the atoms in the molecule.
Gram formula mass. The mass of one mole of an ionic
compound is equal to the sum of the mass of the atoms in the
The term Molar Mass can be used to refer to the mass of 1
Mol of any element or compound
Question 12 p. 150
Question 13 p. 151
Question 14 p.153
Mole – Mass conversion
The Molar Mass can be used as a conversion factor to convert
grams of a substance into moles of that substance
Lets work that through…
Lets imagine we have 7.20 moles of the compound
dinitrogen trioxide. How much does that weigh?
First, lets work out the molecular mass of one mole of
dinitrogen trioxide (N2O3)
2 mol N x 14.0 g N/1 mol N = 28.0g N
3 mol O x 16.0 g O/1 mol O = 48g O
1 mol of N2O3 = 28.0 + 48.0 = 76.0 g N2O3
Our conversion factor is:
1 mol N2O3 = 76.0g of N2O3
Or 1 mol N2O3 / 76g N2O3
Or 76 g N2O3 / 1 mol N2O3
Known = 7.60 mol N2O3 unknown = mass
Conversion mole -> mass
Conversion factor = 76 g N2O3 / 1 mol N2O3
7.20 mol N2O3 x 76 g N2O3 / 1 mol N2O3
= 5.47 x 102 g N2O3
Lets practice more!
Question 18 a, b, f
Question 19 a, c, g
The volume of a mole of gas
Standard Temperature and Pressure (STP) = 0°C and 1 atm
At STP the volume of 1 mole of any gas is 22.4L
This can be used as a conversion factor!
Questions 20-21 p.158
Question 23 p.159
Density is the amount of mass in a given volume.
The density of gases is measured in g/L
The density can be used as a conversion factor to calculate
the molar mass of a gas.
If you know the mass of 1L, you can calculate the mass of
Using gas density
Imagine you know that the density of a compound containing
carbon and oxygen is 1.96 g/L at STP. Is the gas CO or CO2?
The volume of both gases at STP is 22.4.
The molar mass must be:
22.4L of gas x 1.96g = 43.9g of unknown gas
The molar mass of CO is 12.0g C +16.0g O = 28.0g
The molar mass of CO2 is 12.0g C + 16.0g O = 44.0g
Therefore the gas must be CO2
Give Question 23 on p.159 a try!
Converting between units using
Questions 24-27 p.161
Question 48-52 p.171