In the reaction system between Cobalt (11) chloride and ammonia, the net reactio

ID: 704872 • Letter: I

Question

In the reaction system between Cobalt (11) chloride and ammonia, the net reaction that occurs is shown below as an equilibrium process: A student conducted three experiments to fully characterize this reaction. The first of which was an equilibrium experiment. Experiment 1 The student saw from observation that this reaction has a favorable equilibrium constant, as the reaction proceeded toward the product. The student manipulated the equilibrium conditions to put the ammonia in a large excess of the cobaltous ion. This allowed the student to assume that the cobaltous ion was the limiting reactant. The student then collected data to generate a calibration curve. Standards for Callibration Curve NH3] 0.050 [Co+21 0.0010 Total Volume 1.00 1.00 1.00 1.00 1.00 1.00 2.00 3.00 4.00 5.00 10.00 10.00 10.00 10.00 10.00 0.665 1.330 1.995 2.660 3.325 The student then created an unknown sample to determine the equilibrium constant. The initial component of the solution are shown in Table 2 below. Equilibrium Measurements INH3 10.50 ? | Co+210.10 M | Total v l Absorbance 1.00 10.00 1.00 0.0532 1 Use the data shown from both experiments to determine the equilibrium constant for the hexamminecobalt () chloride

Explanation / Answer

As cobaltous ion is the limiting reagent therefore number of moles of cobalt complex produced is equal to number of moles of cobaltous ion reacted.

Concentration of complex (M)

Absorbance

0.0010/10 = 0.00010

0.665

(0.0010×2)/10 =0.0002

1.330

(0.0010×3)/10 = 0.0003

1.995

(0.0010×4)/10 = 0.0004

2.660

(0.0010×5)/10 = 0.0005

3.325

From the above calibration curve, it has been found that concentration of the unknown sample correspond to absorbance value of 0.0532 is 8×10-6 (M).

So equilibrium constant K = [Co(NH3)6Cl2]/[NH3]6[CoCl2]

[CoCl2] = [(0.1)-(8×10-5)]/10 = 9.992×10-3 (M)

[NH3] = [(0.5)-(8×10-5)]/10 = 0.049992 (M)

By putting these values we get K = 5.13×104 (M)-6