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I don’t need you to perform the experiment. I just need help on steps to solve these and how to know when they are oxidizing and reducing in the lab. Also the steps on how to solve part c with step by step. Thank you!

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Elin HesselLv2
27 Sep 2019

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Related questions

I do not need you to perform the experiment. I need to help know how to identify the oxidation and reduction products in the problem and how to know by the evidence. And how to find part c for the products. Thanks so much for your help

I'm trying to find the amount of ethanol in an unkown solution by titration but I'm having trouble calculating it. Molarity of thiosulfate: 0.0806 M, amount of dichromate used: 15 mL

here is what my lab manual says:

The titration is based on the oxidation of ethanol with an oxidizing agent, such as potassium dichromate. Depending on the solution pH and the amount of potassium dichromate added, ethanol can be oxidized to ethanal (acetaldehyde, CH3CHO) via reaction 1, or to ethanoic acid (acetic acid, CH3COOH) via reaction 2:

3C2H5OH(aq) + Cr2O72-(aq) + 8H+ ? 3CH3CHO(aq) + 2Cr3+(aq) + 7H2O (1)

3C2H5OH(aq) + 2Cr2O72- (aq) + 16H+ ? 3CH3COOH(aq) + 4Cr3+ (aq) + 11H2O (2)

In order to ensure all ethanol has completely reacted via reaction 2, a known and excess amount of potassium dichromate (let’s call it potassium dichromate total) is added into a sample solution containing ethanol. The amount of unreacted potassium dichromate is then determined by reacting with potassium iodide solution via reaction 3 to form iodine:

Cr2O72- (aq) + 14H+ + 6I-(aq) ? 2Cr3+ (aq) + 7H2O(l) + 3I2 (aq) (3)

From the reaction 3, we know that 1 mole of dichromate ions can produce 3 moles of I2. Therefore, we just need to determine how much moles of I2 is produced in reaction 3, then, we can get the moles of unreacted potassium dichromate. Subtracting the moles of unreacted potassium dichromate from the moles of potassium dichromate total gives the moles of potassium dichromate that have reacted with ethanol. Then, from the stoichiometry of reaction 2, one should be able to know how much ethanol is in the test solution.

How to know the moles of I2 produced in reaction 3? The I2 is titrated with sodium thiosulfate (Na2S2O3) via the following reaction 4:

I2(aq) + 2S2O32-(aq) ? 2I-(aq) + S4O62-(aq) (4)

Experimental data: For the standardization of thiosulfate it took 31.7 mL of thiosulfate to reach the end point, for the unknown solution, it took 23.85 mL of thiosulfate to reach the endpoint. How do I use these numbers to find the amount of ethanol in the unknown solution?

Take four test tubes from the Containers shelf and place them on the workbench.

Fill each test tube with a different halide solution from the Materials shelf, as directed below. You may want to label the test tubes by double-clicking on each test tube and renaming it.

Test Tube # Halide Solution

1 10.5 mL 0.1 M sodium chloride

2 10.5 mL 0.1 M sodium fluoride

3 10.5 mL 0.1 M sodium iodide

4 10.5 mL 0.2 M potassium bromide

Take 0.5 M calcium nitrate from the Materials shelf and add 4.5 mL to each of the four test tubes. You may want to use the + or – zoom buttons in the lower right of the screen for a closer view. Record any evidence of a reaction with each of the four halide ions in your Lab Notes. Remember to press Save Notes.

Dispose of the four test tubes by dragging them to the recycling bin beneath Experiment 1: Observe the Reactions Between Halide and Calcium Ions

the workbench.

Experiment 2: Observe the Reactions Between Halide and Silver Ions

Prepare another set of four test tubes with the halogen ions as described in steps 1 and 2 of experiment 1.

Take 0.1 M silver nitrate from the Materials shelf and add 4.5 mL to each of the four test tubes. Observe and record any evidence of a reaction with each of the four halide ions in your Lab Notes. You may want to zoom in for a closer look.

Dispose of the four test tubes by placing them in the recycling bin.

Experiment 3: Observe the Reactions Between Silver Halides and Ammonia

Take four 50 mL beakers from the Containers shelf and place them on the workbench.

Fill each beaker with a different halide solution from the Materials shelf, as directed below. You may want to label the beakers by double-clicking on each one and renaming it.

Beaker # Halide Solution

1 10.5 mL 0.1 M sodium chloride

2 10.5 mL 0.1 M sodium fluoride

3 10.5 mL 0.1 M sodium iodide

4 10.5 mL 0.2 M potassium bromide

Take 0.1 M silver nitrate from the Materials shelf and add 4.5 mL to each beaker. Observe and record any evidence of a reaction with each of the four halogen ions in your Lab Notes.

Take 4 M ammonia from the Materials shelf and add 4.5 mL to each beaker. Observe and record any evidence of a reaction with each of the four halogen ions in your Lab Notes.

Dispose of the four beakers by placing them in the recycling bin.

Experiment 4: Observe the Reactions Between Silver Halides and Sodium Thiosulfate

Prepare another set of beakers with the halide ions as described in steps 1 and 2 of experiment 3.

Take 0.1 M silver nitrate from the Materials shelf and add 4.5 mL to each beaker. Observe and record any evidence of a reaction with each of the four halogen ions in your Lab Notes.

Take 0.2 M sodium thiosulfate from the Materials shelf and add 4.5 mL to each beaker. Observe and record any evidence of a reaction with each of the four halogen ions in your Lab Notes.

Dispose of the four beakers by placing them in the recycling bin.

Experiment 5: Identify Unknown Halides

On the Materials shelf, there are two unidentified halide solutions. Each solution contains one of the four halide ions from the previous four experiments. Identify them using the reagents and

Questions

1. Suppose you forgot to label your test tubes and you do not remember their order. Can you identify the sodium fluoride solution using only the reaction with silver nitrate?

a. Yes sodium floride will form a white precipitate with silver nitrate

b. No both sodium floride and potassium bromide will form a yello precipitate with silver

c. Yes sodium floride will not form a precipitate with silver nitrate

d. No sodium floride does not form a precipate with silver nitrate

2. How can you identify the sodium chloride containing test tube using only the reactions with silver nitrate?

a. Sodium chloride does not form a white pecipate with silver nitrate

b. Sodium chloride forms a pale yellow precipitate with silver nitrate

c. Sodium chloride forms a yellow precipate with silver

d. Sodium chloride forms a white precipate with silver nitrate

3. Which of the following statements are true?

a. Silver nitrate fomed precipates in the presence of floride,bromide and iodine ions

b. Silver nitrate formed precipates in the presence of chloride, bromide, and fluoride ions

c. Silver nitrate fomed precipates in the presence of chloride, floride, and iodine ions

d. Silver nitrate fomed precipitaes in the prensence of chloride,bromide and iodine ions

4. If you were allowed to react your unknown halides with only one of the reagents used in this lab, which reagent will you pick and why?

a. Ammonia because it forms colored precipitaes with both halides

b. Silver nitrate because it forms different color precipitates with the two halides

c. Calcium nitrate because it forms a precipate with only one of the halides

d. Sodium thiosulfate because it changes the color of the halide solutions

5. How would you expect the results to change if the identity of the cation were to change?

a. There would be increased solubility in the prensence of ammonia

b. There would be no change since these test are for the halide ion

c. The next change of the solution would increase

d. There would be increased precipation of the halide ion upon the addition of silver nitrate

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