Experiment III: Kinetics Pre-Lab Questions 1. Please provide the balanced net io

Question

Experiment III: Kinetics Pre-Lab Questions 1. Please provide the balanced net ionic equations for the following reactions: a. KI in aqueous solution

b. (NH4)2S2O8 in aqueous solution

c. KI and (NH4)2S2O8 in aqueous solution

i. If starch is added to the solution initially, what color will the final solution be and what causes this color change?

d. Na2S2O3 in aqueous solution

e. If Na2S2O3 is added to the solution in part c, what reactions will occur? Indicate the color of each side of each reaction

. 2. The rate law for the reaction A + B ? Products was found to be rate = k[A][B]2. a. What is the reaction order with respect to A?

b. What is the reaction order with respect to B?

c. What is the overall order of the reaction?

d. If the concentration of A is doubled while B is left unchanged, what happens to the rate of the reaction?

e. If the concentration of B is doubled while A remains unchanged, what happens to the rate of the reaction?

f. What does k represent in the rate law expression? What are the units of k for this reaction?

3. Suppose the following data is obtained for the reaction:

a. Determine the rate law for the reaction.

b. Calculate the rate constant, k, and give the units.

Explanation / Answer

1.

a. net ionic equation,

KI(aq) --> K+(aq) + I-(aq)

b. net ionic equation

(NH4)2S2O8(aq) --> 2NH4+(aq) + S2O8^2-(aq)

c. net ionic equation,

S2O8^2-(aq) + 2I-(aq) --> 2SO4^2-(aq) + I2(aq)

i. The I2 formed in the reaction forms starch-I2 complex which has a purple color. This is after startch addition.

d. net ionic equation,

Na2S2O3(aq) --> 2Na+ + S2O3^2-(aq)

e. reaction occurs as,

I2(aq) + 2S2O3^2-(aq) --> 2I-(aq) + S4O6^2-(aq)

So I2 generated in part c. reacts with S2O3^2- to give colorless solution (violet to colorless). Once all of S2O3^2- in consumed, excess formed I2 in solution would now complex with startch and give a purple coloration to the solution.

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