<Dd> T c = 8 a / (27 R b) (\ displaystyle T_ (c) = 8a / (27Rb)), V c = 3 n b (\ displaystyle V_ (c) = 3nb), p c = a / (27 b 2) (\ displaystyle p_ (c) = a / (27b ^ (2))). </Dd> <P> However, the van der Waals equation, based on a mean field theory, does not hold near the critical point . In particular, it predicts wrong scaling laws . </P> <P> To analyse properties of fluids near the critical point, reduced state variables are sometimes defined relative to the critical properties </P> <Dl> <Dd> T r = T / T c (\ displaystyle T_ (r) = T / T_ (c)), p r = p / p c (\ displaystyle p_ (r) = p / p_ (c)), V r = V R T c / p c (\ displaystyle V_ (r) = (\ frac (V) (RT_ (c) / p_ (c)))). </Dd> </Dl>

1. which of the following are pure substances (1 point)