# What is the temperature dependency of the van-der-Waals constants? [closed]

What is the effect of the temperature on the van-der-Waals constants $$a$$ and $$b$$?

I have checked on the effect of pressure and volume on the van-der-Waals constants, but I've not been able to get the effect of temperature.

## closed as unclear what you're asking by andselisk♦, Tyberius, aventurin, Todd Minehardt, M.A.R.Jan 8 at 1:21

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• See, they are constants; they are assumed not to depend on anything. – Ivan Neretin Jan 7 at 14:51

$$a$$ and $$b$$ are supposed to be constants. But, they in fact aren't, so your question is in principle valid.
vdW is not a very good model to describe $$V_m(p,T)$$ of any actual non-ideal gas over a larger pressure or temperature range, and if you take a really good model (those have 6 or 8 parameters), you can just mathematically derive $$a(p,T)$$ and $$b(p,T)$$.
vdW is useful (just like virial coefficents and other models with only two or three parameters) to accurately model $$p,V,T$$ in a limited range without a large computational effort, e.g. for process control.