1. Molar volume
1.1.6
Text Book : Pages
2008 SPECIFICATIONS

2. 1.1.6 Moles and Gas Volumes
Calculate the amount of substance in moles using gas volumes

3. 24 dm3 One mole of different gases
ONE MOLE OF ANY GAS OR VAPOUR OCCUPIES
24 dm3
. . . at room temperature and pressure
rtp = room temperature and pressure (298K and 105 Pa)
One mole of different gases

4. MOLAR VOLUME rtp = standard temperature and pressure (298K and 105 Pa)
ONE MOLE OF ANY GAS OR VAPOUR OCCUPIES 24 dm3 at rtp
1. Calculate the volume occupied by 0.25 mols of carbon dioxide at rtp
1 mol of carbon dioxide will occupy a volume of 24 dm3 at rtp
0.25 mol of carbon dioxide will occupy a volume of 24 x 0.25 dm3 at rtp
0.25 mol of carbon dioxide will occupy a volume of 6 dm3 at rtp
rtp = standard temperature and pressure (298K and 105 Pa)
ONE MOLE OF ANY GAS OR VAPOUR OCCUPIES 24dm3 at room temperature and pressure

5. ONE MOLE OF ANY GAS OR VAPOUR OCCUPIES 24dm3 at rtp
MOLAR VOLUME
ONE MOLE OF ANY GAS OR VAPOUR OCCUPIES 24dm3 at rtp
1. Calculate the volume occupied by 0.25 mols of carbon dioxide at rtp
1 mol of carbon dioxide will occupy a volume of 24 dm3 at rtp
0.25 mol of carbon dioxide will occupy a volume of 24 x 0.25 dm3 at rtp
0.25 mol of carbon dioxide will occupy a volume of 6.0 dm3 at rtp
2. Calculate the volume occupied by 0.08g of methane (CH4) at rtp
Relative Molecular Mass of CH4 = (4x1.0) = 16.0
Molar Mass of CH4 = g mol-1
Moles = mass/molar mass 0.08g / 16.0 g mol = mols
1 mol of methane will occupy a volume of 24 dm3 at rtp
0.005 mol of methane will occupy a volume of 24 x dm3 at rtp
0.005 mol of methane will occupy a volume of dm3 at rtp
that’s 120 cm3
ONE MOLE OF ANY GAS OR VAPOUR OCCUPIES 24dm3 at room temperature and pressure

6. MOLES = volume THE MOLAR VOLUME MOLAR volume
CALCULATING THE NUMBER OF MOLES OF A SINGLE SUBSTANCE
moles = vol / molar vol
volume = moles x molar volume
molar volume = volume / moles
UNITS
volume dm3 ( litres ) or cm3
molar volume dm or 24,000 cm3
MOLES = volume
MOLAR volume
Volume
dm3
MOLES x 24.dm3
COVER UP THE VALUE YOU WANT AND THE METHOD OF CALCULATION IS REVEALED

7. 1.1.6 Tasks
Write out these Key definitions
Molar volume is . . .
Examiner tip is
Worksheets
Questions : 1, 2, 3

8. cm cm3
cm cm3
cm cm3
cm cm3
cm cm3
cm cm3
cm cm3
8 96 cm cm3
cm cm3
cm cm3
Volume
dm3
MOLES x 24.dm3

9. 1
8.33E-03 2
2.08E-02 3
4.17E-02 4
8.33E-02 5
9.75E-03 6
9.42E-03 7
1.07E-02 8 9 10
1.00E-01 11
2.92E-02 12
2.33E-01 13
9.17E-02 14
8.75E-03 15
3.33E-02 16
3.33E-03 17
8.30E-05 18
8.33E-01 19
1.75E-02 20
3.75E-02
0.0417
0.0833
0.0107
0.1
0.233
0.0917
0.0333
0.833
0.0175
0.0375
Volume
dm3
MOLES x 24.dm3

10. Volume
dm3
MOLES x 24.dm3
mass
MOLES x Molar mass

11. dm3 MOLES x 24.dm3 MOLES x Molar mass Volume mass 1 1090 2 7050 3
85700 4
7490 5
701 6
670 7
3380 8
30000 9 10
180000 11
56000 12
30500 13
20300 14
16000 15
5260 16
2370 17
375 18
12000 19
26500 20
77100
Volume
dm3
MOLES x 24.dm3
mass
MOLES x Molar mass

12. dm3 MOLES x 24.dm3 MOLES x Molar mass Volume mass 1 159 2 64 3 80 4 7128 7 30 8
58.1 9 32 10
27.9 11
34.03 12
16.97 13
38.02 14
27.98 15
43.97 16
31.92 17
210.96 18
36.48 19
81.12 20
128.06
Volume
dm3
MOLES x 24.dm3
mass
MOLES x Molar mass

13. Volume
dm3
MOLES x 24.dm3
mass
MOLES x Molar mass

14. So what is the molar volume of a gas ? . . rearrange and calculate !
Extension . . Why . . .
Combined and ideal gas laws
p V = n R T
p is the pressure – Pa that’s actually – 101,325 Nm-2
V is the volume – m that’s 100 x 100 x cm3
n is the number of moles of gas – that just 1
T is the temperature measured in Kelvin – rtp is 298K
R is the gas constant  ( (15) J K-1 mol-1 )
So what is the molar volume of a gas ? . .
rearrange and calculate !
The unit can be cm3 or dm3

15. V = n R T p
p V = n R T
V = x 1 x 298
101,325 =
X1,000,000 ( convert to cm3)
= 24, 453 cm3
That's about dm3