Simulating a Job's plot. Consider the reaction , for which K [AB₂]/[A][B^]2. Suppose that the following mixtures of A and B at a fixed total concentration of 104M are prepared:

(a) Prepare a spreadsheet to find the concentration of AB₂ for each mixture, for equilibrium constants of K = 10⁶, 10⁷, and 108. One way to do this is to enter the values of [A]total and [B]total in columns A and B, respectively. Then put a trial (guessed) value of [AB2] in column C. From the mass balances [A]_total = [A] + [AB₂] and [B]_total + [B] - 2[AB₂], we can write K = [AB₂]/[A][B]² = [AB₂]/{([A]_total - [AB₂])([B]_total - 2[AB2])²}. In column D, enter the reaction quotient [AB₂]/[A][B]². For example, cell D2 has the formula "=C2/((A2-C2)(B2-2*C2)^2)". Then vary the value of [AB₂] in cell C2 with Solver until the reaction quotient in cell D2 is equal to the desired equilibrium constant (such as 10⁸).

(b) Prepare a graph by the method of continuous variation in which you plot [AB₂] versus mole fraction of A for each equilibrium constant. Explain the shapes of the curves.

[Alotal (M) otl (M) At (M t M) 1.00 2.00 2.50 x 3.00 10-5 3.33 10-5 4.00 x 10-56.00x 10-5 10-5 10-5 9.00 10- 8.00 10-5 5.00 10-5 10-5 5.00 x 10-5 4.00 10-5 6.00 x 7.00 x 10 X 10 7.50 x 10 5 3.00 x 10 7.00 10-5 8.00 10-5 6.6710-51 9.0010 2.00 10-5 1.00 10-5 -5