## Z ni dyi

Explain why direct division of (1) by Zni does not yield (3).

7.11 1 mole of pure A at 400 K is mixed with 3 moles of an A-B solution with 33% B at

600 K. Assume that mixing is adiabatic and that A-B solutions follow Regular solution theory with Q = +30 kJ/mole. The heat capacities of pure components A and B are 30 and 50 J/mole-K, respectively.

(a) What is the temperature of the final solution?

(b) What is the entropy change in the process?

7.12 The activity coefficient of component A of an A-B binary solution is given by:

where C and D are constants.

What is the activity coefficient of component B?

Note: the A-B mixture does not follow regular solution theory.

7.13 The activity coefficient of component A of an A-B solution is given by:

where E and F are constants. Student #l claims that the equation for lnyB can be obtained simply by interchanging the subscripts A and B in the equation for lnyA,. Student #2 says that this is wrong, and she can prove it. Show the proof that student #2 has in mind.

7.14 Calculate the entropy change when one mole of pure A is added to 4 moles of an equimolar A-B solution at the same temperature. Assume ideal mixing.

7.15 Give two reasons why the following is not an acceptable formula for describing the activity coefficient of component A in a binary A-B mixture. 