The color change accompanying the reaction of phenolphthalein with strong base is illustrated below. The change in concentration of the dye can be followed by spectrophotometry (Section 4.9), and some data collected by that approach are given below. The initial concentrations were [phenolphthalein] = 0.0050 mol/L and [OH ‒ ] = 0.61 mol/L. (Data are taken from review materials for kinetics at chemed.chem.purdue.edu.) (For more details on this reaction see L Nicholson, Journal of Chemical Education, Vol. 66, p. 725, 1989.) (a) Plot the data above as [phenolphthalein] versus time, and determine the average rate from t = 0 to t = 15 seconds and from t = 100 seconds to t = 125 seconds. Does the rate change? If so, why? (b) Use a graphical method to determine the order of the reaction with respect to phenolphthalein. Write the rate law, and determine the rate constant. (c) What is the half-life for the reaction?
The color change accompanying the reaction of phenolphthalein with strong base is illustrated below. The change in concentration of the dye can be followed by spectrophotometry (Section 4.9), and some data collected by that approach are given below. The initial concentrations were [phenolphthalein] = 0.0050 mol/L and [OH ‒ ] = 0.61 mol/L. (Data are taken from review materials for kinetics at chemed.chem.purdue.edu.) (For more details on this reaction see L Nicholson, Journal of Chemical Education, Vol. 66, p. 725, 1989.) (a) Plot the data above as [phenolphthalein] versus time, and determine the average rate from t = 0 to t = 15 seconds and from t = 100 seconds to t = 125 seconds. Does the rate change? If so, why? (b) Use a graphical method to determine the order of the reaction with respect to phenolphthalein. Write the rate law, and determine the rate constant. (c) What is the half-life for the reaction?
Solution Summary: The author analyzes the graph plotted between [Phenolphthalein] and time. The average rate of a reaction is defined by the change in concentration of substrate or target (product).
The color change accompanying the reaction of phenolphthalein with strong base is illustrated below. The change in concentration of the dye can be followed by spectrophotometry (Section 4.9), and some data collected by that approach are given below. The initial concentrations were [phenolphthalein] = 0.0050 mol/L and [OH‒] = 0.61 mol/L. (Data are taken from review materials for kinetics at chemed.chem.purdue.edu.) (For more details on this reaction see L Nicholson, Journal of Chemical Education, Vol. 66, p. 725, 1989.)
(a) Plot the data above as [phenolphthalein] versus time, and determine the average rate from t = 0 to t = 15 seconds and from t = 100 seconds to t = 125 seconds. Does the rate change? If so, why?
(b) Use a graphical method to determine the order of the reaction with respect to phenolphthalein. Write the rate law, and determine the rate constant.
With a starting concentration of 4.00 x 10^-3 M ClO2, how much time (in s) will it take up for the compound (ClO2) concentration to reach 1.20 x 10^-3 M? See the image for the given table.
The following reaction was analyzed and data was collected.
3 A (g) + 2 B4 (g) + C2 (g) – D (g)
Initial Concentration (mol L)
(Ba]
0.100
Trial
Initial Rate
(mol Ls4)
9.072 x 109
3.629 x 10
2.449 X 107
3.135 х 10%
[A]
[C:]
1
0.100
0.400
2.
0.400
0.100
0.400
0.100
0.300
0.400
4
0.100
0.600
1.60
0.600
0.75
0.100
a) Determine the rate law and rate constant for the reaction. Be sure to show all of your work.
b) Determine the rate for the fifth reaction.
но
HO
Но
HO
co + ½ 0, -
+ H,O
H"
H
но
Он
ascorbic acid
dehydroascorbic acid
Vitamin C is oxidized slowly to dehydroascorbic acid by the oxygen in air. It is catalyzed by ions such as
Cu*2 and Fe*3. The reaction can be followed by measuring the ultraviolet absorbance at 243 nm.
Time (hours)
Absorbance (A)
1/A
In A
- In A
0.75
1.3
-0.29
0.29
1
0.38
2.6
-0.97
0.97
0.19
5.3
- 1.7
1.7
3
0.095
11
- 2.4
2.4
27. Which of the following is the best interpretation of the data given above?
(A) The data support a zero-order reaction.
(B) The data support a first-order reaction.
(C) The data support a second-order reaction.
(D) The overall order is third.
28. A new compound is synthesized and found to be a monoprotic acid with a molar mass of 248
g/mole. When 0.0050 moles of this acid are dissolved in 0.500L of water, the pH is measured as 2.94.
What is the pk, of this acid?
(A)
(В)
(C)
(D)
2.33
3.89
5.78
7.78
29. What is the hybridization of carbon 1 (far left) and carbon 2 (middle) in this…
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