1. Part A.4. Describe the chemistry that was occurring in the experiment between the time when solution A and B were mixed and Stop time.
Answer; Solution A and solution B were reacting with one another in order to create a compound with both starch and iodide. Once the solution had formed, a deep blue color was shown.
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2. Part A. 4. For kinetic trial 2, Alicia was distracted when the color change occurred but decided to record the time lapse read from her watch. Will this distraction cause an increase or decrease in the slope of the log (rate) versus log [I–]o? Explain
Answer;If you have a reaction involving A, with an order of n with respect to A, the rate equation says: Rate = k [A]n
If you take the log of each side of the equation, you get:
Log(rate) = log k + n log [A]
This second equation would plot as a straight line with slope n. If you measure the slope of this line, you get the order of the reaction. As rate is independent of initial concentration, so its slope will not increase or decrease and will remain constant.
3. Part A, Table 24.1.
a. When doing the kinetic trials, Susan forgot to include the deionized water. Will this omission hasten or delay the formation of the blue color in the trials (exclusive of Trial 6)? Explain.
In the reaction initially iodide, under acidic conditions and in the presence of molybdate catalyst, reacts with hydrogen peroxide to give iodine gas.I2 then binds with I- iodide present in the solution to form triiodide which forms blue complex with starch.
H2O2 + 2 KI + H2SO4 → I2 + K2SO4 + 2 H2O
If deionized water is not added then the concentration of KI will be high , but it will react with H2O2 in the stoichometric ratio of 1:1 only,so H2O2 works as limiting reagent as it is lesser in concentration,thereby controlling the amount of I2 produced. So the amount of triiodide will not change, but the rate of reaction will increase for
I +I-↔I3- as rate of reaction is dependent on initial concentration of reactants.
As triiodide will form faster so faster will it react with starch giving blue colored complex.
b. When doing the kinetic trials, Oscar mistakenly omitted the sodium thiosulfate solution. How will this omission change the appearance of the resultant solution (from the mixing solutions A and B) from that of a correctly completed experiment? Explain your reasoning.
There will be no color change because the sodium thiosulfate plays an
important role in causing the chemical change when it mixed with the
c. When doing the kinetic trials, Peyton mistakenly omitted the starch solution from the kinetic trials. How will this omission change the appearance of the resultant solution (from the mixing solutions A and B) from that of a correctly completed experiment? Explain your reasoning.
Without the starch solution there would be no color change in the reaction,
which would completely change the reaction
d. Of the three chemists above, which chemist will have the most accurate results? Explain.
4. Part C.2. Review the plotted data.
a. What is the numerical value of the y-intercept?
b. What is the kinetic interpretation of the value for the y-intercept?
It is the point in which the color change begins to start, where there no other
c. What does its value equal in equation 24.8?
C equals log k + log [I– ] p
5. State the effect that each of the following changes has on the reaction rate in this experiment—increase, decrease, or
no effect. (Assume no volume change for any of the concentration changes.)
a. An increase in the H2O2 concentration. Explain.
An increase in the concentration of H2O2 would increase the rate of the
reaction because it is a strong reactant and more molecules in the solution
means that there is more of a chance that they will react.
b. An increase in the volume of water in solution A. Explain.
An increase in the volume of water in solution will cause a decrease in the
rate of reaction because the solution is being more diluted
c. An increase in the Na2S2O3 concentration. Explain.
An increase in the Na2S2O3 concentration will have no effect on the
reaction rate because in reaction rate=k[I-][H2O2], S2O3 is not in either
d. The substitution of a 0.5% starch solution for one at 0.2%. Explain
A substitution of 0.5% starch solution for one of 0.2% will not change the
rate of reaction because it is not directly proportional to the rate reaction
6. If 0.2 M KI replaced the 0.3 M KI in this experiment, how would this affect the following—increase, decrease, or no effect?
a. The rate of the reaction. Explain
Will decrease because it depends on the amount of substance
b. The slopes of the graphs used to determine p and q. Explain
The slopes would not change because it represents the rate contestant,
therefore, it is independent of the concentration of reactants
c. The value of the reaction rate constant. Explain.reported activation energy for the reaction—too high or too low? Explain
The value of the reaction rate would not change, for it is represented in the slope,
therefore, rate constant does not change with decreasing
8. Part E.4. Arnie’s data plot has a greater negative slope than Bill’s. Which student will record the higher activation energy for the reaction? Describe your reasoning
Arnie’s data plot will have the higher activation energy because negative slope will
have greater the activation energy slope as opposed to a positive slope