Experiment 2: Using the Secondary Standard to Determine the Concentration of an Acid

1. In an Erlenmeyer flask, add 25 mL of Unknown #1 concentration of acetic acid (CH₃COOH) and 2 drops of phenolphthalein indicator.

2. Coarse Titration:

(a) Take a burette from the Containers shelf and place it on the workbench. Fill the burette with 50 mL of the standardized sodium hydroxide solution. Record the initial burette reading. Place the Erlenmeyer flaskon the lower half of the burette.

(b) Perform a coarse titration, adding large increments of the sodium hydroxide solution from the buretteby pressing and holding the black knob at the bottom of the burette. Each time you add the sodium hydroxide solution, check the volume remaining in the burette. As the sodium hydroxide is added to the acetic acid solution the pH increases. Watch for a change of the phenolphthalein color in the Erlenmeyer flask. The pink color will appear in Erlenmeyer flask when the endpoint is either reached or crossed. Record the burette volume at which this occurs.

(c) Place the Erlenmeyer flask and the burette in the recycling bin.

3. Fine Titration:

(a) Set up the tiration as before: (i) An Erlenmeyer flask filled with 25 mL of unknown #1 concentration of acetic acid and 2 drops of phenolphthalein indicator. (ii) A burette filled with 50 mL of the standardizedsodium hydroxide solution. Record the initial burette reading. (iii) Place the Erlenmeyer flask on the lower half of the burette.

(b) Click and hold the black knob of the burette to quickly add enough standard sodium hydroxide solution to just get into the range of the coarse titration: 1 mL BEFORE the pink endpoint. This is near, but not yet at, the titration's endpoint.

(c) Add sodium hydroxide solution in small increments, down to one drop at a time, record the volume of the pink endpoint.

(d) Place the Erlenmeyer flask and the burette in the recycling bin.

4. Repeat the titration two more times for a total of three trials. Use 30mL of acetic acid for trial 2 and 35mL for trial 3. Calculate the acid concentration of each trial.
[If you run out of NaOH, simply prepare a second solution as described in step 2 of Exp. 1. You don’t need to standardize it a second time. Assume the standardized concentration is the same as before.]

In the space below, show your calculation(s) for approximating the molarity of a 200.0 mL solution containing 0.8 g NaOH so molarity of NaOH is 0.10mol/L?

Need help with the B, C, D, E, F, G and the calculation part

Trial 1              Trial 2              Trial 3

a) Volume of acid (mL)                                     25.1mL             30.1mL            35.1mL

b) Volume of NaOH titrated (mL)                     _____              _____              _____

c) Moles of NaOH titrated                                 _____              _____              _____

d) Moles of acid                                               _____              _____              _____

e) Concentration of acid (M)                             _____              _____              _____

f) Average acid concentration (M)                                             _____

Using your Trial 1 data, show you work for calculating each of the following:

Moles of NaOH titrated

Moles of acid

Concentration of acid

In an experiment in extrasensory perception (ESP), a subject in one room is asked to state the color (red or blue) of a card chosen from a deck of 50 well-shuffled cards by an individual in another room. It is unknown to the subject how many red or blue cards are in the deck.

a.)

What are your null and alternate hypotheses in this case?

b.)

If the subject identifies 32 cards correctly, determine the chances of each hypothesis being correct. Use the Gaussian approximation to the binomial distribution in making your calculations. Are these results are significant at either the 5% and 1% levels?

In an experiment, a solution sulfuric acid is mixed with an excess of sodium carbonate. One of the products is a gas. This gas is collected in a one-liter flask at 20.0°C. What will be the pressure in the flask if 113 mL of the sulfuric acid solution is used? The [H2SO4] can be found from its complete titration (25.0 mL H2SO4) with 16.0 mL of NaOH (NaOH : standardized with 58.7 mL of a 1.000 M HCl)

To test whether memory changes with age, a researcher conducts an experiment in which there are four groups of six subjects each. The four groups are listed below. All subjects are in good health and matched in other important variables such as years of education, IQ, gender and motivation. Each subject is shown a series of nonsense syllables (a meaningless combination of three letters such as DAF or FUM) at a rate of one syllable every 4 seconds. The series is shown twice after which the subjects are asked to write down as many of the syllables as they can remember. The number of syllables remembered by each subject is shown below.

Please use SPSS to compute the test statistic for the following problems. For those questions, please turn in the appropriate SPSS output.

1. Perform the appropriate analysis
2. Wherever appropriate, calculate and report effect size(s)
3. Make a decision regarding the null hypothesis and write an APA-style conclusion interpreting your statistical results with regard to the aims of the experiment and as you would write it up in a report, including the statistical evidence to back it up.

In an experiment involving the breaking strength of a certain type of thread used in personal flotation devices, one batch of thread was subjected to a heat treatment for 60 seconds and another batch was treated for 120 seconds. The breaking strengths (in N) of ten threads in each batch were measured. The results were 60 seconds: 43 52 52 58 49 52 41 52 56 58 120 seconds: 59 55 59 66 62 55 57 66 66 51 Let μX represent the population mean for threads treated for 120 seconds and let μY represent the population mean for threads treated for 60 seconds. Find a 99% confidence interval for the difference μX−μY . Round down the degrees of freedom to the nearest integer and round the answers to three decimal places.

The 99% confidence interval is

In order to determine the possible effect of chemical treatment on women’s hair, an experiment was conducted. The results are given in the accompanying table

1. a) State the null hypothesis and the alternative hypothesis

2. b) Calculate (and show) the expected frequency for each cell. Place each expected value in parentheses ( ) in the same cell (and to the right) as the observed value to which it corresponds

3. c) Using the formula: X^2= ∑(O-E)^2/(E)  calculate the chi-square value.

4. d) At the 5% level of significance, what is the chi-square critical value?

5. e) What decision would you make?

6. f) Draw a conclusion (in the context of the problem)?

In calculating the percent yield for this experiment, which of following the statements is/are correct?

An experiment studied the efficacy of using 95% ethanol or 20% bleach as a disinfectant in removing bacterial and fungal contamination when culturing plant tissues. The experiment was repeated 15 times with each disinfectant, using eggplant as the plant tissue being cultured. Five cuttings per plant were placed on a petri dish for each disinfectant and stored at 25°C for four weeks. The observation reported was the number of uncontaminated eggplant cuttings after the four-week storage.

(a) Are you willing to assume that the underlying variances are equal?

Yes

No    

(b) Using the information from part (a), are you willing to conclude that there is a significant difference in the mean numbers of uncontaminated eggplants for the two disinfectants tested? (Use μ₁ for 95% ethanol disinfectant and μ₂ for 20% bleach disinfectant. Use α = 0.05.)

State the null and alternative hypotheses.

H₀: (μ₁ − μ₂) < 0 versus H_a: (μ₁ − μ₂) > 0

H₀: (μ₁ − μ₂) = 0 versus H_a: (μ₁ − μ₂) ≠ 0    

H₀: (μ₁ − μ₂) = 0 versus H_a: (μ₁ − μ₂) > 0

H₀: (μ₁ − μ₂) = 0 versus H_a: (μ₁ − μ₂) < 0

H₀: (μ₁ − μ₂) ≠ 0 versus H_a: (μ₁ − μ₂) = 0

State the test statistic. (Round your answer to three decimal places.)
t =  

State the p-value.

p-value < 0.010

0.010 < p-value < 0.020    

0.020 < p-value < 0.050

0.050 < p-value < 0.100

0.100 < p-value < 0.200

p-value > 0.200

State the conclusion.

H₀ is rejected. There is insufficient evidence to conclude that there is a significant difference in the mean numbers of uncontaminated eggplants for the two disinfectants used.

H₀ is not rejected. There is sufficient evidence to conclude that there is a significant difference in the mean numbers of uncontaminated eggplants for the two disinfectants used.    

H₀ is not rejected. There is insufficient evidence to conclude that there is a significant difference in the mean numbers of uncontaminated eggplants for the two disinfectants used.

H₀ is rejected. There is sufficient evidence to conclude that there is a significant difference in the mean numbers of uncontaminated eggplants for the two disinfectants used.

This isn't a homework assignment more of a search for advice. The lab experiment that my group is conducting is to separate two mixtures, a solid-solid and a liquid-liquid mixture. Each mixture has 2 separate components. The solid-solid mixture was easy enough, a quick solvent extraction completely separated the two and soon we will do IR, NMR and melting point determination to try to identify the solids.

The liquids however are another problem all in themselves. The mixture is tinted yellow and is translucent. The two liquids are entirely miscible and there seems to be no obvious phycial way to separate them. There is nothing known about the liquids currently except what we've measured;

The mixture is neutral pH

The mixture has at least one aromatic comound

We've been unable to observe a major polarity difference in the mixture, we had time to run 2 TLC plates, one with polar eluent and one with a mixed 75/25 polar/non-polar eluent. The Rf values have overlapped on both so we believe the compounds have similar polarities, we plan on running a few more with different eluents. This is also why we've been unable to determine whether both compounds are aromatic or only one is.

There is a good chance that the compounds are constitutional isomers of each other based on the hints that our TA has been dropping. We're extremely reluctant to attempt a distillation because as far as we can tell the polarities are extremely similar, as it is directly related to boiling point it is unlikely that the boiling points will be different enough to separate the compounds without a professional distillation set-up. We only have microscale organic kits to work with and previous distillations using the kit resulted in major loss of compound if there is any separation at all.

The rules state we cannot use more than 5mL of the unknown mixture total, for all of the tests we utilize. As a result we cannot afford to lose any to faulty processes like distillation.

The Characterizational techniques we are experienced in using are IR, Melting point, boiling point, refractive index, polarimetry. We are NOT allowed to use Mass Spec. and we can ONLY use NMR after we can prove that we are reasonably confident in the identity of our unknowns.

We're out of ideas so we're hoping for some solid advice and discussion. Thank you!

Tools we have access to are;

TLC

Staining Agents

UV lights

Sep. Funnel

Microscale Distillation (not recommended)

Essentially unlimited glassware

Hot plates and ice-baths

Reagents: HCl, NaOH, Sodium Anhydride, various solvents: toluene, hexanes, ethyl acetate, diethyl ether, water, ethanol, methanol.

I highlighted any relevant information regarding the liquids.