1. Moles, Volume and Density

2. C11-3-12 MOLAR CALCULATIONS
OUTCOME QUESTION(S):
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 
STP

3. Avogadro ( )
Equal volumes of different gases (held at the same temperature and pressure) contain the same number of moles.
Volume depends on pressure, temperature and particles – if conditions are the same they must have the same number of particles
10 particles
10 particles

4. Chemists measure gas volume at a Standard Temperature and Pressure (STP) of OoC and kPa (1 atm).
At STP: 1 mole (or 6.02 x 1023 particles) of any gas occupies 22.4 L - called the molar volume.

5. Moles are now the converting factor between mass, volume and number of particles

6. This will take one step…
How many moles are in 50.0 L of Fluorine gas at
STP?
50.0 L
22.4 L
1 mol
= 2.23 mol
This will take one step…

7. This will take two steps…
What is the STP volume of 10.0 g of Methane gas?
CH4 = 16.0 g/mol
10.0 g
16.0 g
1 mol
1 mol
22.4 L
= L
This will take two steps…

8. Often related in: grams (g) per litre grams per mL (or cm3)
Density: A physical (qualitative) property that describes the mass per unit volume of a substance.
Often related in: grams (g) per litre
grams per mL (or cm3)
Density is a relationship between mass and volume – how could we use this as a conversion factor?

9. Density converts mass and volume – this is very important for gases that are NOT at STP

10. 1 mole when not at STP is different
Calculate the volume, in litres, of one mole of
ammonia (NH3) at room temperature if the density
is g/L.
NOT at STP – can’t use 22.4 L
NH3 = 17.0 g/mol
1 mol
1 mol
17.0 g
0.696 g
1 L
= L
Notice volume of
1 mole when not at STP is different
(in this case larger)
density

11. Calculate the volume, in litres, of two moles of carbon dioxide, at room temperature, when the density is 1.80 g/L.
CO2 = 44.0 g/mol
2 mol
1 mol
44.0 g
1.80 g
1 L
= L
density

12. C11-3-12 MOLAR CALCULATIONS
CAN YOU / HAVE YOU?
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 
STP