Hello; i'm having some difficulties with a thermo question of mine. at low density water vapor conforms well to the ideal gas equation provided the temp is higher than about 320K, but the heat capacity is a function of temperature. The following formula gives the specific heat capacity at constant volume, as a function of T cv = 1273.0 + 0.3441T + (2.833x10^-4)T^2 J/kgK a) calculate the entropy change for 1kg of water vapour heated from 350K to 1000K at constant volume. Here's what i did; S = (integral)dQ/T = (integral)NcvdT/T. Where N = (m/MM) = 1/0.018 I subbed cv into this equation then divided it by T = (m/MM)(1273.0/T + 0.3441 + (2.833x10^-4)T)dT Then integrated over T1 = 350, T2 = 1000 to get: S = (1/0.018)(1273.0(ln(1000/350)) + 0.3441(1000-350) + ((2.833x10^-4)/2)(1000-350)^2) however, my answer is not correct according to the back of the book. The answer is supposed to be 1.68kJ/K. Where did i go wrong? b) Same as a) except at constant pressure. here's what i tried; S = (inegral)(Ncpdt) where cp = cv + R hwoever this also doesn't give me the correct answer. Any help or suggestions would be greatly appreciated!