Calculations involving gas volumes
3 marks · EasyA student collects three different gases at rtp in three identical flasks. Data for the gases is shown below:
| Gas | Volume collected (dm³) | Moles collected |
|---|---|---|
| Argon | 1.0 | ? |
| Oxygen | 0.5 | ? |
| Hydrogen | 2.0 | ? |
Calculate the number of moles of argon collected.
Calculate the number of moles of oxygen collected.
Which gas sample contains the largest number of molecules? Explain your answer.
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.
Show answer
(a) 0.042
(b) 0.021
(c) Hydrogen; because it has the largest volume, so also the greatest number of moles and molecules. · must show Identifies hydrogen, Links volume and number of molecules for gases at rtp
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Marking points
B1 (a) · 1 mark · Correctly calculates or states number of moles of argon: 1.0 / 24 = 0.042 (accept 0.0417)
B2 (b) · 1 mark · Correctly calculates or states number of moles of oxygen: 0.5 / 24 = 0.021 (accept 0.0208)
B3 (c) · 1 mark · Chooses hydrogen and gives correct reasoning (largest volume = most moles = most molecules for gases at rtp).
Worked solution
a) n (Ar) = 1.0 / 24 = 0.042 mol
b) n (O₂) = 0.5 / 24 = 0.021 mol
c) Hydrogen: it has the greatest volume, so (by Avogadro's law) contains the largest number of molecules.