This lab experiment is on the preparation of benzoic acid: a Grignard reaction.
In the procedure: following the addition of carbon dioxide; then 6M HCL(aq); diethyl ether was added and the aqueous layer discarded; then 6M NaOH(aq) was added and the ether layer discarded; Finally, concentrated HCL(aq) was added and a precepitate formed, which was filtered and rinsed with cold deionized H2O. The purpose of these steps was to isolate, and thus purify, benzoic acid from both water-soluble and organic-soluble impurities.
a) Provide a balanced equation for each step after the addition of CO2.
b) State the impurities being removed in each step after the addition of CO2.
In questions 1a and 1b; identify the phase (i.e. organic or aqueous) that each compound is in
In: Chemistry
An experiment is conducted to determine if classes offered in an online format are as effective as classes offered in a traditional classroom setting. Students were randomly assigned to one of the two teaching methods. Data below.
a. Test the claim that the standard deviations for the two groups are equal. What is the p-value of the test?
b. Construct a 95% confidence interval on the difference in expected final exam scores between the two groups. Does the data support the claim that there is no difference?
| On-line | Classroom |
| 77 | 79 |
| 66 | 64 |
| 70 | 88 |
| 79 | 80 |
| 76 | 66 |
| 58 | 81 |
| 54 | 71 |
| 72 | 84 |
| 56 | 77 |
| 82 | 76 |
| 90 | 89 |
| 68 | 62 |
| 59 | 74 |
| 67 | 68 |
| 71 | 98 |
| 74 | 77 |
| 72 | 65 |
| 62 | 83 |
| 77 | |
| 78 | |
| 76 | |
| 57 | |
| 67 | |
| 69 | |
| 82 | |
| 78 | |
| 80 | |
| 61 | |
| 77 | |
| 65 | |
| 71 | |
| 76 | |
| 58 | |
| 82 | |
| 78 | |
| 74 |
In: Statistics and Probability
In an experiment to measure the wavelength of light using two slits, it is found that the interference fringes are too close together to easily count them. To spread out the fringe pattern, one could…
A. Increase the slit separation
B. Decrease the slit separation
C. Increase the distance from the slits to the viewing screen
D. Decrease the distance from the slits to the viewing screen
E. Both increasing the distance from the slits to the viewing screen and increasing the slit separation would work
F. Both increasing the distance from the slits to the viewing screen and decreasing the slit separation would work
In: Physics
In an experiment, a group of students will determine the dielectric constant of paper. They have the following materials available, as well as other materials traditionally available in a high school physics lab.
(a) Outline an effective experimental procedure to gather the necessary data that can be used to determine the dielectric constant of paper. Place a check mark next to each item above that the students should use. Draw a labeled diagram to represent the setup used for this procedure.
The table below shows data from a different experiment in which students measure the capacitance of different setups as they vary the distance between the two plates of the capacitor, the area of the plates, and the material inserted between the plates.
| Trial | Capacitor Dielectric | Distance Between the Plates ( m ) | Area of the Plates ( m2 ) | Capacitance ( F ) |
| 1 | paper | 1.00×10−4 | 0.04 | 8.1×10−9 |
| 2 | paper | 1.00×10−4 | 0.09 | 18.3×10−9 |
| 3 | paper | 1.00×10−4 | 0.16 | 32.6×10−9 |
| 4 | paper | 1.00×10−4 | 0.25 | 49.8×10−9 |
| 5 | paper | 2.00×10−4 | 0.25 | 23.1×10−9 |
| 6 | paper | 3.00×10−4 | 0.25 | 18.9×10−9 |
| 7 | paper | 4.00×10−4 | 0.25 | 14.9×10−9 |
| 8 | paper | 5.00×10−4 | 0.25 | 9.2×10−9 |
| 9 | plastic | 1.10×10−4 | 0.04 | 11.3×10−9 |
| 10 | plastic | 1.10×10−4 | 0.09 | 25.3×10−9 |
| 11 | plastic | 1.10×10−4 | 0.16 | 45.1×10−9 |
| 12 | plastic | 1.10×10−4 | 0.25 | 70.4×10−9 |
| 13 | plastic | 2.20×10−4 | 0.25 | 35.2×10−9 |
| 14 | plastic | 3.30×10−4 | 0.25 | 23.5×10−9 |
| 15 | plastic | 4.40×10−4 | 0.25 | 17.6×10−9 |
| 16 | plastic | 5.50×10−4 | 0.25 | 14.1×10−9 |
(b)
i. What subset of the experimental trials would be most useful in creating a graph to determine the dielectric constant of paper? Explain why the selected trials are most useful.
ii. Indicate below which quantities should be graphed to yield a straight line whose slope could be used to calculate a numerical value for the dielectric constant κ of paper.
Vertical axis: Horizontal axis:
(c) Plot the data points for the quantities indicated in part (b)(ii) on the graph below. Clearly scale and label all axes including units, if appropriate. Draw a straight line that best represents the data.
(d) Use the data to determine a value for κ of paper.
(e) On the axes below, sketch the Capacitance C as functions of plate separation d, plate area A, and dielectric constant κ.
In: Physics
In an experiment to determine the effect of nutrition on the attention spans of elementary school students, a group of 45 students is divided into three groups of 15, and randomly assigned to each of three meal plans: no breakfast, light breakfast, and full breakfast. Their attention spans, in minutes, were recorded. Say you want to test the hypothesis that the means of the attention spans are not all the same at a level of significance of 5%.
(a) (3 pts) What are the null and alternative hypotheses?
(b) (4 pts) Suppose that you find MSG=26 and MSE=3.1. Find the F-statistic, and estimate the p-value of your data using the F-table.
(c) (3 pts) Should you accept or reject? Explain.
In: Statistics and Probability
An experiment was conducted to test the effect of a new drug on a viral infection. After the infection was induced in 100 mice, the mice were randomly split into two groups of 50. The control group received no treatment for the infection, while the other group received the drug. After a 30-day period, the proportions of survivors, p̂1 and p̂2, in the two groups were found to be 0.38 and 0.66, respectively. (a) Is there sufficient evidence to indicate that the drug is effective in treating the viral infection? Use α = 0.05. State the null and alternative hypotheses. H0: (p1 − p2) < 0 versus Ha: (p1 − p2) > 0 H0: (p1 − p2) = 0 versus Ha: (p1 − p2) > 0 H0: (p1 − p2) = 0 versus Ha: (p1 − p2) < 0 H0: (p1 − p2) = 0 versus Ha: (p1 − p2) ≠ 0 H0: (p1 − p2) ≠ 0 versus Ha: (p1 − p2) = 0 Find the test statistic and rejection region. (Round your answers to two decimal places. If the test is one-tailed, enter NONE for the unused region.) test statistic z = rejection region z > z < State your conclusion. H0 is rejected. There is sufficient evidence to indicate that the drug is effective in treating the viral infection. H0 is not rejected. There is insufficient evidence to indicate that the drug is effective in treating the viral infection. H0 is rejected. There is insufficient evidence to indicate that the drug is effective in treating the viral infection. H0 is not rejected. There is sufficient evidence to indicate that the drug is effective in treating the viral infection. (b) Use a 95% confidence interval to estimate the actual difference (p1 − p2) in the survival rates for the treated versus the control groups. (Round your answers to three decimal places.) to
In: Statistics and Probability
The project is to "Design and build an experiment to verify the first law of thermodynamics by stirring air with an electric motor powered paddle, in a well-insulated container." We are planning on finding the work of the motor and seeing if it equal to the change in internal energy of the container. The only problem is that we are confused on how to find the internal energy. What would be the best/easiest way to solve this? Also since the containor is well insulated does that mean that the deltaQ would equal 0?
Thank you very much!
In: Mechanical Engineering
An experiment was carried out to investigate the effect of species (factor A, with
I = 4)
and grade (factor B, with
J = 3)
on breaking strength of wood specimens. One observation was made for each species—grade combination—resulting in SSA = 443.0, SSB = 424.6, and SSE = 125.4. Assume that an additive model is appropriate.
(a)
Test
H0: α1 = α2 = α3 = α4 = 0
(no differences in true average strength due to species) versus
Ha: at least one αi ≠ 0
using a level 0.05 test.
Calculate the test statistic. (Round your answer to two decimal places.)
f = 1
What can be said about the P-value for the test?
P-value > 0.1000.050 < P-value < 0.100 0.010 < P-value < 0.0500.001 < P-value < 0.010P-value < 0.001
State the conclusion in the problem context.
Reject H0. The data does not suggest any difference in the true average strength due to species.Reject H0. The data suggests that true average strength of at least one of the species is different from the others. Fail to reject H0. The data suggests that true average strength of at least one of the species is different from the others.Fail to reject H0. The data does not suggest any difference in the true average strength due to species.
(b)
Test
H0: β1 = β2 = β3 = 0
(no differences in true average strength due to grade) versus
Ha: at least one βj ≠ 0
using a level 0.05 test.
Calculate the test statistic. (Round your answer to two decimal places.)
f = 4
What can be said about the P-value for the test?
P-value > 0.1000.050 < P-value < 0.100 0.010 < P-value < 0.0500.001 < P-value < 0.010P-value < 0.001
State the conclusion in the problem context.
Reject H0. The data does not suggest any difference in the true average strength due to grade.Fail to reject H0. The data does not suggest any difference in the true average strength due to grade. Reject H0. The data suggests that true average strength of at least one of the grades is different from the others.Fail to reject H0. The data suggests that true average strength of at least one of the grades is different from the others.
In: Statistics and Probability
In order to compare a new variety of wheat with a standard, an experiment is used with six plots receiving the new variety and ten plots receiving the standard. The yields (t/ha) are as follows:
New variety: 2.6 2.1 2.5 2.4 1.9 2.3
Standard variety: 1.7 2.1 2.0 1.8 2.3 1.6 2.0 2.1 2.2 1.9
Question : (a) Identify the model for comparing the wheat yield?
(b) Is there evidence at the 5% significance level that the yield of the new variety is higher?
ANSWER QUESTION (a) necessary.
In: Statistics and Probability
what is the main purpose of this experiment? and how to analyze the data, what are we trying to get? and how this experiment is working?
Kinetics of the Oxidation of Benzyl Alcohol
Objective: To study the kinetics of a reaction by a spectrometric method and how this relates to the dynamics of the system.
Theory
The oxidation of benzyl alcohol by the permanganate ion in acidic media is: 2MnO4 + 5C6H5CH2OH + 6H → 2Mn + 5C6H5CHO + 8H2O
The balanced equation does not provide any information concerning the reaction kinetics or dynamics. Indeed, the reaction does not progress to products by the simultaneous combination of all the reactants in their stoichiometric ratios. Rather, the reaction progresses through several simpler steps where the stoichiomentric coefficients indicate the order of the reaction with respect to that reactant. The mechanism describing the reaction often involves reactants not accounted for in the overall reaction. A typical mechanism1 for this oxidation involves a hydride transfer from the alcohol:
H+ + MnO4 ↔ HMnO4 {fast equilibrium}
HMnO4 + C6H5CH2OH → H2MnO4- + C6H5CHOH+ {slow}
C6H5CHOH+ → C6H5CHO + H+ {fast}
H2MnO4- → products {fast}
Notice the speed at which a step occurs is indicated and that the slowest step determines the overall rate of the reaction.
The above mechanism is conjecture until it is supported through experiment. Support for this mechanism is achieved by measuring the orders with respect to the reactants and demonstrating that these orders, in conjunction with the proposed rate determining step, agree with the suggested dynamics.
Experimental Setup
The chemical reaction studied will be the oxidation of benzyl alcohol by acid permanganate with the formation of benzaldehyde. According to the proposed mechanism, the kinetics should be of first order with respect to each reactant and will be determined by the spectrometric method using a Varian Spectrometer. A general schematic UV-Vis spectrometer is shown in figure 1. The basic parts of a spectrophotometer are a light source (often an incandescent bulb for the visible wavelengths, or a deuterium arc lamp in the ultraviolet), a holder for the sample, a diffraction grating or monochromator to separate the different wavelengths of light, and a detector. The method used in this experiment is a modification of the method proposed by Liu2.
The samples that you will prepare hold both the acid and alcohol concentrations in such excess that the pseudo first order kinetics is observed. You will be able to determine the order with respect to the remaining reactants from analysis of the rate constants as a function of concentration of the remaining reactants.
The samples that you will prepare hold both the acid and alcohol concentrations in such excess that the pseudo first order kinetics is observed. You will be able to determine the order with respect to the remaining reactants from analysis of the rate constants as a function of concentration of the remaining reactants.
Figure 1. General Schematic UV-Vis Spectrometer.
Procedure
Preparing the solution. Prepare 50 ml of 0.002 M potassium permanganate solution and store it in a brown bottle. The other solutions necessary for this experiment is a 0.04 M Benzyl alcohol and 1.4 M Sulfuric Acid, both of which are already prepared.
Preparing the sample. Absorption/time profiles on seven samples will be measured using the Varian UV-vis spectrometer. The concentrations of those samples are:
|
Sample |
Volume of KMnO4 (ml) |
Volume of C6H5CH2OH (ml) |
Volume of H2SO4 (ml) |
Volume of H2O (ml) |
|
1 |
5 |
10 |
10 |
- |
|
2 |
5 |
7 |
10 |
3 |
|
3 |
5 |
5 |
10 |
5 |
Data Analysis
Plot the Absorption/time profiles of your data. Manipulate the data so that you may acquire the rate constant associated with each sample run. It should be obvious that the reaction is first order with respect to the permanganate ion. Determine the orders with respect to the remaining reactants and verify the proposed mechanism.
In: Chemistry