# Ranking gases by value of the van der Waals equation-of-state constant 'a'? [closed]

How can I find out which gas has the highest value of the van der Waals constant $a$?

Example set of gases in ascending order of $a$: $\ce{NO2}$, $\ce{CO2}$, $\ce{H2}$, $\ce{H2O}$ and $\ce{CCl4}$.

## closed as off-topic by ron, Todd Minehardt, Geoff Hutchison, ringo, Martin - マーチン♦Mar 1 '16 at 4:08

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• Taken from your comment to Max' answer, I think what you are really asking is how you can determine the value of a for any gas without looking it up. I think that would be a valid question. However, now your question was treated as if it was a homework question, because as it is posed, you simply have to look up the values. Hence it is not a good fit for our format. I recommend editing your question, so that it can be reopened and properly answered. – Martin - マーチン Mar 1 '16 at 4:13