1. The problem statement, all variables and given/known data what is the entropy of 1.0 litre of gasoues n2 at Ta=350 K and Pa=2.0 bar given that So = 191.61 J/(K gmol) at To = 298.15 K and Po = 1 bar? 2. Relevant equations I think : S(at 350) - So = NC_p ln (Ta/To) - NR ln(Pa/po) 3. The attempt at a solution My problem is, C_p is not given and can we use this formula if p is not constant.