A 3.0 L cylinder holds nitrogen at 250 kPa…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A L cylinder holds nitrogen at kPa. A L cylinder holds helium at kPa. Both are at the same temperature. A valve between them is opened and the gases mix. The temperature does not change. Find the partial pressure of each gas, the total pressure, and the mole fraction of nitrogen.
Need a reminder? The key ideaShow
Each gas in a mixture fills the whole volume. Its partial pressure is . The total pressure is the sum:
A real gas has below when the pull between molecules wins and above when their size wins.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Nitrogen. It spreads from L into L, so kPa.
Step 2. Helium. kPa.
Step 3. Total. kPa.
Step 4. Mole fraction. .
Answer: kPa, kPa, kPa in all, and a nitrogen mole fraction of .
Watch out. The average of kPa and kPa is kPa. That is wrong, because the larger cylinder holds the gas at the lower pressure.
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