So I need to find the concentration of I2(aq) The reactions are; 2I-(aq)+S2O82--->2SO42-+I2(aq) 2S2O32-(aq)+I2(aq)-->S4O62-(aq)+2I-(aq) The concentration for KI is 0.0401 mol/L, for(NH4)2S2O8 is 0.0602mol/L and for Na2S2O3 is4.17x10-4mol/L. 4.04 mL of KI, 4.04 mL of(NH4)2S2O8, 2.01 mL ofNa2S2O3 are used I know I should be using the second equation, I find the molesfor I2 but I cannot figure the concentration

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rubyyak737Lv1

6 Nov 2019

So I need to find the concentration of I_2(aq)

The reactions are;

2I^-(aq)+S₂O₈^2--->2SO₄^2-+I_2(aq)

2S₂O_3^2-(aq)+I_2(aq)-->S₄O₆^2-(aq)+2I^-(aq)

The concentration for KI is 0.0401 mol/L, for(NH₄)₂S₂O₈ is 0.0602mol/L and for Na₂S₂O₃ is4.17x10^-4mol/L.

4.04 mL of KI, 4.04 mL of(NH₄)₂S₂O_8, 2.01 mL ofNa₂S₂O₃ are used

I know I should be using the second equation, I find the molesfor I₂ but I cannot figure the concentration

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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) + Cr₂O₇^2-(aq) + 8H⁺ ? 3CH₃CHO(aq) + 2Cr³⁺(aq) + 7H₂O (1)

3C₂H₅OH(aq) + 2Cr₂O₇^2- (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 (letâs 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:

Cr₂O₇^2- (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) + 2S₂O₃^2-(aq) ? 2I^-(aq) + S₄O₆^2-(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?

brownplatypus349

Chemical Kenetics

Trial 1

Flask A

25ml of 0.2 M Potassium Iodide (ml) and Volume of 0.2% starch(ml) were added together,

Flask B

25 ml of volume 0.2M Ammonium Persulfate and volume of 0.01 M sodium Thiosulfate(ml) were added together,

After adding flask A and B together, after 20 sec the solution turned from clear to black.

Trial 2

Flask A

25ml of 0.2 M Potassium Iodide (ml) and Volume of 0.2% starch(ml) were added together,

Flask B

12.5ml of 0.2 M Ammonium Persulfate, 12.5ml of 0.2 M Ammonium Sulfate(ml), 10 ml of 0.01 M Sodium Thiosulfate(ml) were added together,

When flask A and B were added, after 42 sec, it turned from clear to black.

Trial 3

Flask A

25ml of 0.2 M Potassium Iodide (ml) and Volume of 0.2% starch(ml) were added together,

Flask B

6.25ml of 0.2 M Ammonium Persulfate (ml), 18.75ml of 0.2 M Ammonium Sulfate, and 10ml of 0.01 M sodium Thiosulfate (ml) were added together.

After flask A and B were added together, at a min and 26 sec, it turned from clear to black.

Trial 4

Flask A

12.5ml of 0.2 M Potassium Iodide (ml), 12.5ml of 0.2 M Potassium Nitrate (ml), 5 ml of 0.2% starch were added together,

Flask B

25 ml of 0.2 Ammonium Persulfate, 10ml of 0.01 M Sodium Thiosulfate (ml) were added together

after mixing both A and B together, at 42 seconds, it turned clear to black.

Trial 5

Flask A

6.25ml of 0.2 M Potassium Iodide, 18.75 ml of 0.2 M Potassium Nitrate, 5ml of 0.2% starch were added together.

Flask B

25 ml of 0.2 Ammonium Persulfate, 10ml of 0.01 M Sodium Thiosulfate (ml) were added together,

After adding flask A and B together, after 1 min and 28 sec, it turned from clear to black.

All at the temp 21.5 C

Questions,

1.What was the initial concentration of thiosulfate?

A.0.00165 M

B.0.00154 M

C.0.00077 M

D.0.00134 M

2. What was the rate of reaction in Trial 1? Choose the closest answer.

A.3.13 x 10-5 M s-1

B.3.85 x 10-5 M s-1

C.4.15 x 10-5 M s-1

D.3.99 x 10-5 M s-1

3. What was the concentration of peroxodisulfate in Trial 1?

A.0.0569 M

B.0.0769 M

C.0.0669 M

D.0.0879 M

4. What was the concentration of iodide in Trial 1?

A.0.0769 M

B. 0.0659 M

C. 0.0869 M

D.0.0571 M

5. What is the order of peroxodisulfate in the rate expression?

A.0

B.2

C.1.5

D.1

6. What is the order of iodide in the rate expression?

A.0

B.2

C.1

D.3

7. What is the rate law for this reaction?

A.rate = k[I-]3[S2O82-]

B.rate = k[I-]2[S2O82-]

C.rate = k[I-][S2O82-]

D.rate = k[I-]1.5[S2O82-]

8. What is the average rate constant? Choose the closest answer.

A.5.44 x 10-3 L/(mol s)

B.5.73 x 10-3 L/(mol s)

C.6.88 x 10-3 L/(mol s)

D.6.16 x 10-3 L/(mol s)

9. The following reaction is second order with respect to A and zero order with respect to B. Identify the correct rate expression.

2A + B -> C + 2D

A.rate = k[A]4

B.rate = k[2A]2

C.rate = k[A]2

D.rate = k[A]2[B]

10. What is the overall reaction order for a reaction with the following rate expression?

rate = k[A]2[B]

A.3

B.1

C.2

D.4

11.A plot of log(rate) versus log[A] yields the following linear equation. What order is the reaction with respect to A?

y = 1.9x + 3.1

A.5

B.2

C.3

D.1.5

12. The iodine clock experiment, which consists of the following three reactions, is set up so [S2O32-] < [S2O82-]. What would happen if [S2O32-] > [S2O82-]?

Reaction 1: 3I- (aq) + S2O82- (aq) ->I3- (aq) + 2SO42- (aq) slow

Reaction 2: I3- (aq) + 2S2O32- (aq) -> 3I- (aq) + S4O62- (aq) fast

Reaction 3: I3- (aq) + starch (aq) -> 3I- ---- starch (bluish black) fast

A.No bluish black color would form because all the I- formed in reaction 1 would be converted back into I3-.

B.The bluish black color would be darker because more S2O32- is present.

C.The bluish black color would be darker because more S2O32- is present.

D.No bluish black color would form because all the I3- formed in reaction 1 would be converted back into I-.

13. The iodine clock experiment consists of the following three reactions, where reaction 1 is slow relative to reactions 2 and 3. Predict what would happen if reaction 2 was slow relative to reaction 1 (assume that reaction 3 is still fast).

Reaction 1: 3I- (aq) + S2O82- (aq) -> I3- (aq) + 2SO42- (aq) slow
Reaction 2: I3- (aq) + 2S2O32- (aq) -> 3I- (aq) + S4O62- (aq) fast
Reaction 3: I3- (aq) + starch (aq) -> 3I- ---- starch (bluish black) fast

A.The reaction would turn blue slower because I3- is removed at a slower rate.

B.A color change would appear immediately because I3- would be removed slowly from solution, and would therefore be able to react with starch.

C.The rate of color change would indicate the rate of reaction 3 instead of reaction 1.

D.Reaction 3 would not occur.

14. A student conducting the iodine clock experiment accidentally makes an S2O32- stock solution that is too concentrated. How will this affect the rate measurement?

A.It will take less time for the color to change, which will decrease delta t, resulting in a higher calculated rate.

B.It will take longer for the color to change, which will increase delta t, resulting in a lower calculated rate.

C.It will take less time for the color to change, which will increase delta t, resulting in a lower calculated rate.

D.It will take longer for the color to change, which will increase delta t, resulting in a higher calculated rate.

15. A student conducting the iodine clock experiment accidentally makes an S2O82- stock solution that is too concentrated. How will this affect the rate measurement?

A.Not all of the 2S2O32- will react, which will decrease the calculated rate.

B.Not all of the 2S2O32- will react, which will increase the calculated rate.

C.It will take longer for the color to change, as the reaction takes longer when more reactant is present.

D.It will take less time for the color to change, as rate increases with concentration of reactant.

16. The following reaction is first order. If the rate at [A] = 0.1 M is 3, what will the rate be at [A] = 0.2 M?

A -> B + C

A.4

B.6

C.9

D.3

17. For a zero order reaction, if the concentration of reactant is increased 4-fold, the reaction rate

A.increases four-fold.

B.increases 8-fold.

C.increases 16-fold.

D.remains the same.

18. If 2.3 x 10-3 M product forms in 46 seconds, what is the rate of the reaction?

A.50 M/s

B.2.3 x 10-3 M/s

C.5.0 x 10-5 M/s

D.2.0 x 104 M/s

19. A plot of log(delta [I3-] / delta t) versus log [I-]0 from data in Trials 1, 4, and 5 is shown below. Determine the value of p from the graph.

A.1

B.0.5

C.2

D.1.5

I know I am only supposed to post one question per answer, but I feel they all go into one, and that is alot of repitition, Anything helps, I need calculations to help me learn it, I have many more questions but I feel if I get some, and get a understanding on how to calculate it, then I will be able to do the rest. Thank you so much.

So i did an experiment on kinetics, and we used 20 mL of KI, and 20mL of (NH4)2 (S2O8)^(2-)

I need to find the concentrations of