PART 1
>>Trial 1
Reactant Solution A
10 ml I^-, 5.0 ml S2O3^2-
Reactant Solution B
10 ml S2O8^2-, 1 ml starch
time to react = 10 seconds
>>Trial 2
Reactant Solution A
10 ml I^-, 5.0 ml S2O3^2-
Reactant Solution B
5 ml S2O8^2-, 1 ml starch
time to react = 20 seconds
>>Trial 3
Reactant Solution A
5 ml I^-, 5.0 ml S2O3^2-
Reactant Solution B
10 ml S2O8^2-, 1 ml starch
time to react = 20 seconds
How do trial 2 and 3 in the above table differ? More than one response is possible.
A) Trial 2 has twice as much I– as Trial 3
B) Trial 3 has twice as much S2O82– as Trial 2
C) Trial 3 has half as much S2O32– as Trial 2
D) Trial 2 has half as much starch as Trial 3
I chose A and B for this question
PART 2
Which of the four proposed mechanisms below would be supported by these results? Note: there may be more than one answer.
Mechanism 1:
I^- + I^- > I2^2- (slow)
I2^2- + S2O8^2– > I^2 + SO4^2- (fast)
Mechanism 2:
I2^2- + S2O8^2– > [S2O8xI]^3- (slow)
[S2O8xI]^3- +I^- > I2 + 2SO4^2- (fast)
Mechanism 3:
I^- + S2O8^2– <> [S2O8xI]^3- (fast)
[S2O8xI]^3- + I^- > I2 + 2SO4^2- (slow)
Mechanism 4:
2I^- + S2O8^2– > I2 + 2SO4^2-
I looked at part 2 for a bit and by looking at the slow step and using that to figure out the rate law I think it might be mechanism 2, would this be right?
PART 1:
To determine how trial 2 and 3 differ, we need to compare the quantities of reactants used in each trial. Let's analyze the reactants and their quantities:
Trial 2:
Reactant Solution A: 10 ml I^-
Reactant Solution B: 5 ml S2O8^2-
Trial 3:
Reactant Solution A: 5 ml I^-
Reactant Solution B: 10 ml S2O8^2-
Comparing the two trials:
A) Trial 2 has twice as much I^- as Trial 3:
This statement is incorrect since Trial 2 has the same amount of I^- as Trial 3. Both trials have 10 ml of I^-.
B) Trial 3 has twice as much S2O8^2- as Trial 2:
This statement is correct. Trial 3 has 10 ml of S2O8^2-, while Trial 2 only has 5 ml of S2O8^2-. Therefore, Trial 3 has twice the amount of S2O8^2- compared to Trial 2.
C) Trial 3 has half as much S2O3^2- as Trial 2:
This statement is incorrect since the quantities of S2O3^2- in both trials remain the same. Both trials have 5.0 ml of S2O3^2-.
D) Trial 2 has half as much starch as Trial 3:
This statement is incorrect since both trials contain the same amount of starch. Both trials have 1 ml of starch.
Therefore, the correct answers are B) Trial 3 has twice as much S2O8^2- as Trial 2.
PART 2:
To determine which proposed mechanism is supported by the given results, we need to examine the experimental data and consider the rate-determining steps in each mechanism.
Looking at the data, we can see that Trial 2 and Trial 3 have the same reaction time (20 seconds), which differs from Trial 1 (10 seconds). This indicates that the reaction rate is affected by the change in the reaction conditions.
Analyzing the proposed mechanisms:
Mechanism 1:
This mechanism involves the slow step of I^- + I^- > I2^2-. However, the given conditions do not suggest a change in the concentration of I^-. Therefore, this mechanism is not supported by the results.
Mechanism 2:
This mechanism involves the slow step of I2^2- + S2O8^2– > [S2O8xI]^3-. In Trial 2 and Trial 3, there is a change in the concentration of S2O8^2-. Therefore, this mechanism can explain the difference in reaction rates observed in the experiments.
Mechanism 3:
This mechanism involves the fast step of I^- + S2O8^2– <> [S2O8xI]^3-. However, there is no indication of an equilibrium reaction in the given data. Therefore, this mechanism is not supported by the results.
Mechanism 4:
This mechanism does not involve any reaction steps that correspond to the observed changes in the reaction conditions. Therefore, this mechanism is not supported by the results.
Based on the analysis, it is correct to conclude that the supported mechanism is Mechanism 2.