Question
1/2 mole CCl4 @ 25 C was mixed with 1/2 mole CH2Cl2 @ 25C. The final T was 27 C. Calculate delta S mixing, delta S for CCl4 on heating, delta S for CH2Cl2 on heating, and delta S system. Assume 131.8 J/K for Cp for CCl4 and 100.0 J/K for Cp for CH2Cl2.
Answers
DrBob222
I assume that is 131.8 and 100.0 J/K*mol.
dS<sub>mix</sub> =
-R(n<sub>i</sub>*ln x<sub>i</sub> where n<sub>i</sub> and x<sub>i</sub> stand for mols and mol faction of the components.
dS<sub>mix</sub> = -8.314[(1*0.5*ln 0.5) + (1*0.5*ln 0.5)] = +5.763 J/K
q CCl4 = mass x Cp x (Tf-Ti)
q = 0.5 mol x 131.8 J/K*mol x 2 = 131.8 J
dS = q/299 = 0.441 J/K.
q CH2Cl2 = 0.5 mol x 100.0 x 2 = 100.0 J
dS = q/299 = 0.334 J/K.
dS<sub>system</sub> = 5.763 + 0.441 + 0.334 = 6.538 J/K.
dS<sub>mix</sub> =
-R(n<sub>i</sub>*ln x<sub>i</sub> where n<sub>i</sub> and x<sub>i</sub> stand for mols and mol faction of the components.
dS<sub>mix</sub> = -8.314[(1*0.5*ln 0.5) + (1*0.5*ln 0.5)] = +5.763 J/K
q CCl4 = mass x Cp x (Tf-Ti)
q = 0.5 mol x 131.8 J/K*mol x 2 = 131.8 J
dS = q/299 = 0.441 J/K.
q CH2Cl2 = 0.5 mol x 100.0 x 2 = 100.0 J
dS = q/299 = 0.334 J/K.
dS<sub>system</sub> = 5.763 + 0.441 + 0.334 = 6.538 J/K.