Kinetics Reaction Lab

Introduction/Background:

Kinetics is the study of how fast chemical reactions occur and the mechanisms of them2. The rate law relates the rate of a reaction to the concentrations of reactants (and catalysts) raised to various powers. The rate law is shown in Equation 11. Rate = k[A]x[B]y[C]z (Eq.1)

The rate constant (k) is a proportionality constant in the relationship between rate and concentrations, but changes when temperature changes.

The effect of temperature on a reaction rate is given by the Arrhenius equation2 (Equation 2):

k=Ae-Ea/RT (Eq.2) where A is the collision frequency factor, Ea the activation energy of the reaction, T the absolute temperature, and R the ideal gas constant.

This experiment

This is done with various volumes of solutions in each run. The temperature remains constant at room temperature.

Part C is determining the effect of temperature on the reaction rate. To observe the effect of temperature, the solutions are bathed in different water temperatures before mixing. This is timed, as well, to determine the activation energy. The reagents, KI and (NH4)2S2O8 are kept constant.

Part D is determining the effect of copper(II) nitrate, a catalyst, on the reaction rate. The temperature remains constant at room temperature. Referencing Table 4 (Flask B), the (NH4)2S2O8 solution doubled while the (NH4)2SO4 decreased in reagent added. One drop of Cu(NO3)2 was added to the mixture. The copper(II) nitrate (catalyst) was added to the flask containing Na2S2O and KI (also known as Flask A).

The constant temperatures were set at room temperature of 20° C, which inevitably helped determine the effect of [S2O82-] on the reaction rate. For the trials on Data Sheet 2 the average reaction time for Run 5 is 41.6 seconds, Run 6 is 82.9 seconds, Run 7 is 138.55 seconds, and Run 8 is 261.3 seconds. The constant temperatures were also set at 20° C, which helped determine the effect of [I- ] on the reaction rate. For the trials on Data Sheet 3 the average reaction time for Run 9 is 277.46 seconds, Run 10 is 159.52 seconds, Run 11 is 86.93 seconds, Run 12 is 44.2 seconds. The constant temperatures varied, as this part of the experiment was determining the effect of temperature on the reaction rate.. In Data Sheet 3 Run 9 has a temperatures consistency of 11° C, Run 10 is at normal room temperature of 19.8° C, Run 11 is set at a higher temperature at about 35° C, and Run 12 is set at the highest temperature at 45° C, overall affecting the reaction rate. Lastly, Data Sheet 4 has the average reaction of 33.08 seconds for Run 13, Run 14 is 28.88 seconds, Run 15 is 74.85 seconds, and Run 16 is 129.45 seconds. During runs 13-16, the constant temperatures were back to normal standards of 20° C, which led to determining the effect of copper(II) nitrate, a catalyst, on the reaction