1. The overall order for the reaction, A+B→C, is 2. A student tests this by measuring the reaction rate at one concentration of A and B, then doubling both concentrations at the same time and re-measuring the rate, which quadrupled. The student concludes that the data support the hypothesis that the above rate law is rate=k[A][B]. Analyze this.
a. The data do support the hypothesis but each trial should be repeated.
b. The data contradict the hypothesis because the rate should have doubled, not quadrupled. ***
c. The data support the hypothesis but a trial holding one reactant constant is needed.
d. The data contradict the hypothesis but testing by changing a single reactant will verify the hypothesis.
2. Determine the overall reaction order for the reaction, A+B→2C using the table of data below:
Experiment Initial [A]/M Initial [B]/M Initial rate/M s-1
1 0.010 0.040 0.0031
2 0.010 0.020 0.0015
3 0.020 0.020 0.0032
a. 0
b. 1
c. 2
d. 3 ***
2. Here's a better version of the table.
1 | 0.010 | 0.040 | 0.0031
2 | 0.010 | 0.020 | 0.0015
3 | 0.020 | 0.020 | 0.0032
I don't believe either answer is correct. What is your rationale for each?
1. since the order of reaction was 2, I thought it would double.
2. I change my answer to option C. Is that correct?
T 1 & 2: 0.0031 / 0.0015 = k (0.010)^m (0.040)^n / k (0.010)^m (0.020)^n. N = 1
T 2 & 3: 0.0015 / 0.0032 = (0.010/ 0.020)^n. M= 1
m + n = 1 + 1 = 2
Yes, 2c is correct.
On question 1, if you double one reactant that will double the rate. True. But if you double BOTH that will double BOTH and 2 x 2 = 4. So could 1b be correct?
1. To determine the overall order of the reaction, the student performed two trials with different concentrations of A and B. The student measured the reaction rate for the first set of concentrations and then doubled both concentrations simultaneously for the second trial.
The student observed that the rate quadrupled in the second trial compared to the first one. This suggests that the rate is directly proportional to the square of the concentrations of A and B, indicating a rate law of rate = k[A][B], where k is the rate constant.
However, to draw a definitive conclusion, the student should repeat each trial at least one more time to ensure the consistency and reproducibility of the results. So, option a is the correct answer.
2. To determine the overall reaction order, we need to examine how changing the concentrations of A and B affects the rate of reaction. The table of data provided gives the initial concentrations of A and B and their corresponding initial rates.
We can calculate the reaction orders with respect to A and B by comparing the rate ratios when their concentrations change in different experiments. Let's examine two experiments at a time:
- Comparing Experiments 1 and 2, we see that the concentration of B remains constant while the concentration of A remains the same. Despite this change in A, the rate changes by a factor of approximately 0.0015/0.0031 = 0.48, suggesting that the reaction order with respect to A is approximately 1.
- Comparing Experiments 2 and 3, we see that the concentration of A remains constant while the concentration of B doubles. The rate changes by a factor of approximately 0.0015/0.0032 = 0.47, indicating that the reaction order with respect to B is also approximately 1.
Since the sum of the reaction orders with respect to A and B gives us the overall reaction order, which is 1 + 1 = 2, the correct answer is option c.