Question

One more of an ideal gas initially at 27oC and 1 bar pressure is heated and allowed to expand reversibly at a constant pressure until the final temperature is 327oC. For this gas, Cv,m = 2.5R, constant over the temperature range. (Note from SRB: Cv,m is the molar heat capacity. An earlier version of the 5th edition that I used last year used Cv with a bar over it, as we have been doing in class. Sorry for any confusion.). a. Calculate the work w done on the gas in this expansion. b. What are ΔU and ΔH for the process? c. What is the amount of heat q adsorbed by the gas?

Answer 1

1)no of mole = 1 mole , T1 =27+273 = 300 K , T2 = 327 + 273 = 600 K , P = 1 bar   

As we know that Cv = U/ T or U =  Cv * T As T = T₂- T₁ = 600 - 300 = 300K

U = 2.5R * 300 K = 750 R

2) As Cp-C_V= nR =  Cp = R + C_V =  2.5R + R = 3.5 R

Cp = H / T

H = Cp * T = 1050 R

AS the process is adiabatic U = q + W ( as q= 0 for adiabatic process )

therefore w = U = 750 R