Calculations involving gas volumes
2 marks · EasyTwo balloons are filled with different gases at room temperature and pressure (rtp): one has 48 dm³ of helium (He), and the other has 48 dm³ of methane (CH₄).
Explain whether the two balloons contain the same number of particles. Give a reason for your answer.
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Yes, they contain the same number of particles because at rtp, equal volumes of gas contain equal numbers of molecules or atoms (Avogadro's law).
Also accept: Yes, both balloons contain the same number of particles because at rtp, equal volumes of gases contain equal numbers of molecules or atoms.; They both have the same number of particles because 48 dm³ of any gas at rtp contains the same number of molecules or atoms.
Common mistakes: Saying different gases have different numbers of particles because they are different substances.; Confusing number of particles with mass.
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Marking points
B1 · 1 mark · States that the two balloons contain the same number of particles.
B2 · 1 mark · Gives the correct reason: equal volumes of gas at rtp contain equal numbers of molecules/atoms (Avogadro's law).
Worked solution
Both balloons contain the same number of particles.
This is because, according to Avogadro's law, equal volumes of gases at rtp contain equal numbers of molecules or atoms, regardless of the type of gas.