Question

Basic Thermodynamics True and False

Q1). Two vessels of equal volume, pressure, and temperature both containing Ar are connected by a valve a) What is the change in entropy when the valve is opened, allowing a mixing of the two volumes? (5 points) number of moles)? Ifnot, what is the new the other contains vacuum. (10 points) b) Is the AS the same if one of the volumes contained Ar, and the other contained Ne (same AS? (10 points c) Compare the entropy change in (b) to the case when one of the volumes contains Ar, and

Answer 1

Given data: * Entropy Change: - Given that two vessels of equal volume pressure and temperature contains Argon gas. (a) V_a = V_b, P_a = P_b and T_a = T_b When identical gases at identical conditions one mixed, then always, change in Entropy is zero. Delta s = 0 (b) If one is Ar and other is Ne, then there exist change in entropy because they are not identical gases. Change in entropy is given by Delta S/n_total = -R_uni x (Sigma x_i l n x_i) Where n_total = total no. of moles of Ar and Ne \r\n Let no. of moles of Ar = 1 mole and n_Ne = 1 mole Therefore n_total = 1 + 1 = 2 moles x_i = mole fraction = No. of moles of gas/Total no. of moles x_Ar = 1/2, x_Ne = 1/q R_uni = 8.314 J/Mole k Therefore Delta s/2 = -8.314 times {1/2 ln (1/2) + 1/2 ln (1/2)} Delta s/q = -8.134 times ln (1/2) Delta s = 11.5 qJ/k