Question

Q2.1 A gas is represented by the equation of state 1 AB Express A and B in terms of critical constants. 20 points) Hint: Use the expressions for critical behavior. 2.2 Use V- 124 cm/mol, P-50.50 atm and T.-283.1 K for CaH, to calculate the pressure at V-3.2 dm3, T-326 K with the result from Q2.1. (20 points)

Answer 1

P = RT (1/v + A/v^2 + B/v^3) = RT (v^@ + AV + B/v^3) = v^3 = RT/p v^2 + RT/p VA + RT/p B = v^3 minus RT/p v^2 minus RTA/p V minus RTB/p = D ----- (I) v = v_c is critical volume will be a solution = (v minus v_c)^3 = 0 = v^3 minus 2 v^2 v_c + 3 v v^2_c minus v^3_c = 0 ------ (II) substituting T = T_c & P = P_c in (1) = v^3 minus RT_c/P_c v^2 minus RT_c AV/P_c minus R T_c B/P_c = 0 ----- (III) comparing (II) & (III) 3 V_c = R_c/P_c 3 v^2_c = minus RT_c A/p_c = minus 3 v_c A = A = minus V_c minus V^3_c = minus R T_c B/P_c = minus 3 v_c B = B = v^2_c/3