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11 Dec 2019

Crystals of AgBr can be removed from black-and-white photographic film by reacting the AgBr with sodium thiosulfate. AgBr(s) + 2S2O32-(aq) [Ag(S2O3)2]3-(aq) + Br-(aq) What is the equilibrium constant for this dissolving process? The Ksp for AgBr is 5.0E-13. The Kf for Ag(S2O3)23- is 2.9E13.

In order to dissolve 4.5 g of AgBr in 1.0 L of solution, how many moles of Na₂S₂O₃ must be added?

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Silver bromide, AgBr (s), is an essential reagent in black and white film developing. It is,

however, only sparingly soluble in water. AgBr (s) has K = 5.0 Ã 10-13, making it difficult to

rinse AgBr from the film negative with water.

Instead, excess AgBr is removed by an aqueous solution of sodium thiosulfate (Na2S2O3), which forms the complex ion Ag(S2O3)23-:

Ag+ (aq) + 2 S2O32- (aq) Ag(S2O3)23- (aq) Kf = 4.7 Ã 10+13 a) To see how this helps, first determine the molar solubility of AgBr (s) in water.

b) The large formation constant of Ag(S2O3)23- (aq) means that almost all of the silver is complexed with the thiosulfate. To determine how much, calculate the [Ag+] at equilibrium in a 1.0 L solution that initially contains 0.001 M silver ions and 0.200 M sodium thiosulfate. Do so by setting up an ICE table and assuming that x is small compared to 0.200 (but not 0.001). Show that this results in a value of x = [Ag(S2O3)23-] = 0.001. In other words, all of the Ag+ complexes.

c) Your result from part b suggests that no Ag+ remains in solution. This obviously canât be correct, since it would result in an infinitely large reaction quotient that wouldnât be equal to an admittedly large equilibrium constant. To determine the correct [Ag+], use the equilibrium concentrations determined in part b as your initial concentrations in a new ICE table. Then use Kf to determine [Ag+]. [This approach is called a stoichiometric shift and is useful when a reaction starts with only reactants but goes almost to completion. Is essence, we are approaching the equilibrium from the direction of all Ag(S2O3)23- and no Ag+ as opposed to the direction of all Ag+ and no Ag(S2O3)23-.]

d) Before we determine the solubility of AgBr (s) in a thiosulfate solution, we need to know the appropriate equilibrium constant. To find it, determine the value of the equilibrium constant for the reaction:

AgBr (s) + 2 S2O32- (aq) <-->Ag(S2O3)23- (aq) + Br - (aq) Kc = ??

e) Finally, calculate the molar solubility of AgBr (s) in 1.0 M sodium thiosulfate. In other words, what is [Ag(S2O3)23-] for the reaction given in part d when the initial concentration of thiosulfate is 1.0 M?

Show all your steps for calculation questions in order to get full points.

1. (4 pts) The solubility product (K_sp) of the insoluble salt AgBr is 5.0 x 10^-13. Calculate the equilibrium constant for the following reaction: Ag⁺(aq) + Br^-(aq) AgBr(s).

2. (6 pts) A solution is prepared by adding 50.0 mL of 0.050 M HCl to 150.0 mL of 0.10 M HNO₃.

a. Calculate the pH of the solution.

b. Calculate the concentrations of all species in this solution.

3. (4 pts) Calculate the volume of concentrated (12 M) HCl needed to prepare 1-L of a pH = 1.50 solution?

4. (5 pts) Arrange the following 0.10 M solutions in order of most acidic to most basic.

KOH, KCl, KCN, NH₄Cl, HCl

5. (6 pts) Calculate the pH of an aqueous solution containing 1.0 x 10^-2 M HCl and 1.0 x 10^-2 M HCN.

6. (5pts) Carbonate buffers are important in regulating the pH of blood at 7.40. What is the concentration ratio of CO₂ (usually written H₂CO₃) to HCO₃^- in blood at pH=7.40?

H₂CO₃(aq) HCO₃^-(aq) + H⁺(aq) K_a = 4.3 x 10^-7

7. (10 pts) HCN gas, a powerful respiratory inhibitor, is highly toxic. It is a very weak acid (K_a = 6.2 x 10^-10) when dissolved in water. If a 50.00-mL sample of 0.100 M HCN is titrated with 0.100 M NaOH, calculate the pH of the solution:

a. before the titration starts.

b. after 8.00 mL of 0.100 M NaOH has been added.

c. at the half-way point of the titration.

d. at the equivalence point of the titration.

Show all your steps for calculation questions in order to get full points.

1. (4 pts) The solubility product (K_sp) of the insoluble salt AgBr is 5.0 x 10^-13. Calculate the equilibrium constant for the following reaction: Ag⁺(aq) + Br^-(aq) AgBr(s).

2. (6 pts) A solution is prepared by adding 50.0 mL of 0.050 M HCl to 150.0 mL of 0.10 M HNO₃.

a. Calculate the pH of the solution.

b. Calculate the concentrations of all species in this solution.

3. (4 pts) Calculate the volume of concentrated (12 M) HCl needed to prepare 1-L of a pH = 1.50 solution?

4. (5 pts) Arrange the following 0.10 M solutions in order of most acidic to most basic.

KOH, KCl, KCN, NH₄Cl, HCl

5. (6 pts) Calculate the pH of an aqueous solution containing 1.0 x 10^-2 M HCl and 1.0 x 10^-2 M HCN.

6. (5pts) Carbonate buffers are important in regulating the pH of blood at 7.40. What is the concentration ratio of CO₂ (usually written H₂CO₃) to HCO₃^- in blood at pH=7.40?

H₂CO₃(aq) HCO₃^-(aq) + H⁺(aq) K_a = 4.3 x 10^-7

a. before the titration starts.

b. after 8.00 mL of 0.100 M NaOH has been added.

c. at the half-way point of the titration.

d. at the equivalence point of the titration.

e. after 52.00 mL of 0.100 M NaOH has been added.

8. (5 pts) Calculate the K_sp value. For bismuth sulfide (Bi₂S₃), which has a solubility of 1.0 x 10^-15 mol/L at 25â°C.

9. (5 pts) Arrange the following group of salts: in order of most soluble to most insoluble.

AgI (K_sp= 1.5 x 10^-16), CuI (K_sp= 5.0 x 10^-16) and CaSO₄ (K_sp= 6.1x 10^-5)

e. after 52.00 mL of 0.100 M NaOH has been added.

8. (5 pts) Calculate the K_sp value. For bismuth sulfide (Bi₂S₃), which has a solubility of 1.0 x 10^-15 mol/L at 25â°C.

9. (5 pts) Arrange the following group of salts: in order of most soluble to most insoluble.

AgI (K_sp= 1.5 x 10^-16), CuI (K_sp= 5.0 x 10^-16) and CaSO₄ (K_sp= 6.1x 10^-5)

tanbutterfly616

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.

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