Calculating the volume of a certain number of moles
4 marks · NormalThe table shows the number of moles of different gases measured at rtp in a laboratory.
| Gas | Moles |
|---|---|
| Oxygen | 0.25 |
| Neon | 0.50 |
| Argon | 1.00 |
For each gas, state the volume it would occupy at rtp in dm³.
What is the volume in cm³ of 0.50 mol of neon gas at rtp?
Explain why 1.00 mol of argon and 1.00 mol of oxygen have the same volume at rtp.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) — · must show Correctly calculates each volume using dm³
(b) 12,000 cm³
(c) Because 1 mole of any gas at rtp has the same molar volume. · must show States molar volume same for all gases at rtp
Common mistakes: Using wrong values for molar volume; Confusing dm³ and cm³
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Marking points
A1 (a) · 1 mark · Correctly states all three volumes in dm³: O2 = 6, Neon = 12, Argon = 24.
A2 (b) · 1 mark · Correctly calculates and states 12,000 cm³ for neon.
B1 (c) · 1 mark · States (or explains) that all gases occupy the same volume per mole at rtp.
M1 (a) · 1 mark · Method shown or implied for calculation of volume (V = n × 24)
Worked solution
a) Volumes at rtp in dm³:
| Gas | Volume (dm³) |
|---|---|
| Oxygen | 0.25 × 24 = 6 |
| Neon | 0.50 × 24 = 12 |
| Argon | 1.00 × 24 = 24 |
b) Volume of neon in cm³ = 0.50 × 24,000 = 12,000 cm³
c) 1.00 mol of any gas at rtp has the same molar volume (24 dm³), so the volume is the same for both gases.