Iron Silver Equilibrium Study Guide
Experiment 4 Guide Questions for Discussion Iron-Silver Equilibrium
1. Give the balanced net ionic equation for the reaction between Fe2+ and Ag+. What is the chemical formula of the gray precipitate?
Answer:
Fe2+(aq) + Ag+ (aq) Fe3+(aq) + Ag (s) The formula of the precipitate is Ag(s). 2. Give the balanced net ionic equation for the reaction of Fe2+ with Fe(CN)63-. a. What is the chemical formula of the Prussian blue precipitate? b. How does the formation of the Prussian blue precipitate affect the reaction in (1)?
Answer:
Fe2+ + Fe(CN)63- Fe[Fe(CN)6]- a. The formula of the Prussian blue precipitate is [Fe(CN)6]-. b. The formation of the Prussian blue precipitate …show more content…
decreases the [Fe2+], forcing the reaction in (1) to shift towards reactants. 3. Give the balanced net ionic equation for the reaction of Fe3+ and SCN-. c. What is the chemical formula of the blood red complex? d. How does the formation of the blood red complex affect the reaction in (1)?
Answer:
Fe3+ + SCN- FeSCN2+ a. The formula of the blood red complex is FeSCN2+. b. The formation of the blood red complex decreases [Fe3+], forcing the reaction in (1) to shift towards products. 4. Give the balanced net ionic equation for the reaction between Ag+ and Cl-. e. What is the chemical formula of the white precipitate? f. How does the formation of the white precipitate affect the reaction in (1)?
Answer:
Ag+(aq) + Cl-(aq) AgCl(s) a. The chemical formula of the white precipitate is AgCl. b. The formation of the white precipitate decreases [Ag+], forcing the reaction in (1) to shift towards reactants. 5. The fact that Fe2+, Fe3+, and Ag+ are present in the supernate tells us that the range of the Keq for the reaction in (1) is (choose one, and explain): a) Keq> 100 b) Keq< 0.01 c) 0.01<Keq<100
Answer: (c.) 0.01<Keq<100
The components Fe2+, Fe3+, and Ag+ are present in the supernate.
This concludes that the mixture is at equilibrium and Keq cannot exceed to 100 nor it would be less than 0.01.
Copper-Ammonia Equilibrium
6. At the beginning of the reaction between Cu2+ and NH3(when only a few drops of ammonia have been added): g. What is the color of the precipitate formed? h. What is the identity of the precipitate formed? i. Explain how this precipitate formed. Provide the net ionic equation. 7. When the precipitate has dissolved upon addition of more ammonia, what is the color of the solution? What copper complex is responsible for this? 8. Provide the balanced net ionic equation for the formation of this copper complex. 9. Explain how the addition of HCl decolorized the solution. 10. Give the balanced net ionic equation for the reaction responsible for the shift in equilibrium for this system.
Answer: j. (a) a white precipitate is formed (b) caused by the formation of Cu(OH)2 (c) which is described by the equation Cu2+ + 2OH- Cu(OH)2 since ammonia is present as an aqueous solution, thus the reacts w/ the hydroxide part to yield
Cu(OH)2 k. (a) when the concentration of ammonia is considerably high, the solution transforms into a blue solution (b) caused by the formation of Cu(NH3)42+. l. When HCl is added into the solution, [Cl-] increases, adding up to the probability of decreasing [NH3] and then reverted back the solution to its previous color. m. The equation is given by NH4+ + Cl- NH4Cl in which ammonium chloride is present in the solution though it is colorless and cannot be seen directly in the solution but is implied by reverting back to pale blue color of the copper ion. Chromate-Dichromate Equilibrium
11. What is the color of the chromate solution? Of the dichromate solution? 12. Which species (CrO42- or Cr2O72-) changed color when acid was added? when base was added? * Give the balanced net ionic equation for the conversion of chromate to dichromate. * Give the balanced net ionic equation for the conversion of dichromate to chromate. 13. Based on your observation in (12), which species is stable under acidic condition? Under basic condition?
Answer:
n. Chromate solution is yellow; Dichromate solution is orange. o. Chromate solution changed color when acid was added. Dichromate solution changed when base was added. * Conversion of chromate to dichromate: 2CrO42- + 2H+ Cr2O72- + H2O * Conversion of dichromate to chromate: Cr2O72- + 2OH- 2CrO42- +H2O p. Under acidic conditions, Cr2O72- is stable. Under basic conditions, CrO42- is stable.
Iron Thiocyanate Equilibrium
14. Give the balanced equation for the reaction between Fe3+ and SCN-. 15. To which direction the equilibrium shifted when (a) Fe3+, (b) SCN- and (c) NaCl was added? Explain your answer based on your observation during the experiment. 16. For 15c, what reaction caused the observed shift in equilibrium?
Answer:
q. Fe3+ + SCN- + 5H2O [Fe(H2O)5SCN]2+ r. (a) shifted towards products (b) shifted towards products (c) shifted towards reactants s. Fe3+ + 4Cl- FeCl4-
Cobalt-Cobalt Chloride Equilibrium
17. Give the balanced net ionic equation for the reaction between Co2+ and Cl-. 18. What is the color of Co2+? of CoCl42-? 19. Why does the cobalt solution turn purple upon addition of a few drops of HCl? What cobalt species are present in this purple solution? 20. Why does the purple solution turn blue upon addition of more HCl? What cobalt species is responsible for this color? 21. Why does the purple solution turn blue upon heating? (Hint: State whether the reaction is exothermic or endothermic.)
Answers:
t. Co2+ + 4Cl- CoCl42- u. Co2+ is a free ion w/c is not visible in aqueous solutions. CoCl42- has a blue color. v. When adding more HCL, [Cl-] increases but not too high to shift the reaction towards the right side. Purple solution appears to be Co(H2O)62+. w. When adding more HCL, [Cl-] increases up to the extent of shifting the reaction towards the right side. CoCl42- is responsible for the blue color. x. The formation of CoCl42- is an endothermic reaction. Thus if under a high temperature, reaction tends to favour the formation of CoCl42-.
* Error analysis: If you were not able to observe some of the desired results, explain possible sources of discrepancies in the experiment.
The possible discrepancy in the experiment is the failure to come up with the precise amounts of the reagents w/c yield a probable different visual result. The apparatuses that were used might have been contaminated w/ excess reagents, also providing a visual result but with less precision compared to the correct result.
Experiment 4 Guide Questions for Conclusion
1. What are the equilibria studied in this experiment? 2. Was the experiment able to illustrate a) The effect of changing concentrations of reactants/products b) The effect of temperature on equilibrium?
How so? *Be concise. You do not have to repeat the whole discussion to explain how your objectives were met or not met.
Answers:
1. The equilibria involved in the experiment is the (1) Iron-Silver Ion System ; (2) Copper-Ammonia Equilibrium; (3) Chromate-Dichromate Equilibrium ; (4) Iron Thiocyanate Equilibrium and (5) Cobalt Ion equilibrium. 2. (a) The effect of changing concentrations was illustrated by characteristic color changes which signify which formation is favoured.
(b) The effect of temperature is well-illustrated by the cobalt ion equilibrium which showed a change in color due to a favoured, endothermic reaction at the varied temperature.
1. Give the balanced net ionic equation for the reaction between Fe2+ and Ag+. What is the chemical formula of the gray precipitate?
Answer:
Fe2+(aq) + Ag+ (aq) Fe3+(aq) + Ag (s) The formula of the precipitate is Ag(s). 2. Give the balanced net ionic equation for the reaction of Fe2+ with Fe(CN)63-. a. What is the chemical formula of the Prussian blue precipitate? b. How does the formation of the Prussian blue precipitate affect the reaction in (1)?
Answer:
Fe2+ + Fe(CN)63- Fe[Fe(CN)6]- a. The formula of the Prussian blue precipitate is [Fe(CN)6]-. b. The formation of the Prussian blue precipitate …show more content…
decreases the [Fe2+], forcing the reaction in (1) to shift towards reactants. 3. Give the balanced net ionic equation for the reaction of Fe3+ and SCN-. c. What is the chemical formula of the blood red complex? d. How does the formation of the blood red complex affect the reaction in (1)?
Answer:
Fe3+ + SCN- FeSCN2+ a. The formula of the blood red complex is FeSCN2+. b. The formation of the blood red complex decreases [Fe3+], forcing the reaction in (1) to shift towards products. 4. Give the balanced net ionic equation for the reaction between Ag+ and Cl-. e. What is the chemical formula of the white precipitate? f. How does the formation of the white precipitate affect the reaction in (1)?
Answer:
Ag+(aq) + Cl-(aq) AgCl(s) a. The chemical formula of the white precipitate is AgCl. b. The formation of the white precipitate decreases [Ag+], forcing the reaction in (1) to shift towards reactants. 5. The fact that Fe2+, Fe3+, and Ag+ are present in the supernate tells us that the range of the Keq for the reaction in (1) is (choose one, and explain): a) Keq> 100 b) Keq< 0.01 c) 0.01<Keq<100
Answer: (c.) 0.01<Keq<100
The components Fe2+, Fe3+, and Ag+ are present in the supernate.
This concludes that the mixture is at equilibrium and Keq cannot exceed to 100 nor it would be less than 0.01.
Copper-Ammonia Equilibrium
6. At the beginning of the reaction between Cu2+ and NH3(when only a few drops of ammonia have been added): g. What is the color of the precipitate formed? h. What is the identity of the precipitate formed? i. Explain how this precipitate formed. Provide the net ionic equation. 7. When the precipitate has dissolved upon addition of more ammonia, what is the color of the solution? What copper complex is responsible for this? 8. Provide the balanced net ionic equation for the formation of this copper complex. 9. Explain how the addition of HCl decolorized the solution. 10. Give the balanced net ionic equation for the reaction responsible for the shift in equilibrium for this system.
Answer: j. (a) a white precipitate is formed (b) caused by the formation of Cu(OH)2 (c) which is described by the equation Cu2+ + 2OH- Cu(OH)2 since ammonia is present as an aqueous solution, thus the reacts w/ the hydroxide part to yield
Cu(OH)2 k. (a) when the concentration of ammonia is considerably high, the solution transforms into a blue solution (b) caused by the formation of Cu(NH3)42+. l. When HCl is added into the solution, [Cl-] increases, adding up to the probability of decreasing [NH3] and then reverted back the solution to its previous color. m. The equation is given by NH4+ + Cl- NH4Cl in which ammonium chloride is present in the solution though it is colorless and cannot be seen directly in the solution but is implied by reverting back to pale blue color of the copper ion. Chromate-Dichromate Equilibrium
11. What is the color of the chromate solution? Of the dichromate solution? 12. Which species (CrO42- or Cr2O72-) changed color when acid was added? when base was added? * Give the balanced net ionic equation for the conversion of chromate to dichromate. * Give the balanced net ionic equation for the conversion of dichromate to chromate. 13. Based on your observation in (12), which species is stable under acidic condition? Under basic condition?
Answer:
n. Chromate solution is yellow; Dichromate solution is orange. o. Chromate solution changed color when acid was added. Dichromate solution changed when base was added. * Conversion of chromate to dichromate: 2CrO42- + 2H+ Cr2O72- + H2O * Conversion of dichromate to chromate: Cr2O72- + 2OH- 2CrO42- +H2O p. Under acidic conditions, Cr2O72- is stable. Under basic conditions, CrO42- is stable.
Iron Thiocyanate Equilibrium
14. Give the balanced equation for the reaction between Fe3+ and SCN-. 15. To which direction the equilibrium shifted when (a) Fe3+, (b) SCN- and (c) NaCl was added? Explain your answer based on your observation during the experiment. 16. For 15c, what reaction caused the observed shift in equilibrium?
Answer:
q. Fe3+ + SCN- + 5H2O [Fe(H2O)5SCN]2+ r. (a) shifted towards products (b) shifted towards products (c) shifted towards reactants s. Fe3+ + 4Cl- FeCl4-
Cobalt-Cobalt Chloride Equilibrium
17. Give the balanced net ionic equation for the reaction between Co2+ and Cl-. 18. What is the color of Co2+? of CoCl42-? 19. Why does the cobalt solution turn purple upon addition of a few drops of HCl? What cobalt species are present in this purple solution? 20. Why does the purple solution turn blue upon addition of more HCl? What cobalt species is responsible for this color? 21. Why does the purple solution turn blue upon heating? (Hint: State whether the reaction is exothermic or endothermic.)
Answers:
t. Co2+ + 4Cl- CoCl42- u. Co2+ is a free ion w/c is not visible in aqueous solutions. CoCl42- has a blue color. v. When adding more HCL, [Cl-] increases but not too high to shift the reaction towards the right side. Purple solution appears to be Co(H2O)62+. w. When adding more HCL, [Cl-] increases up to the extent of shifting the reaction towards the right side. CoCl42- is responsible for the blue color. x. The formation of CoCl42- is an endothermic reaction. Thus if under a high temperature, reaction tends to favour the formation of CoCl42-.
* Error analysis: If you were not able to observe some of the desired results, explain possible sources of discrepancies in the experiment.
The possible discrepancy in the experiment is the failure to come up with the precise amounts of the reagents w/c yield a probable different visual result. The apparatuses that were used might have been contaminated w/ excess reagents, also providing a visual result but with less precision compared to the correct result.
Experiment 4 Guide Questions for Conclusion
1. What are the equilibria studied in this experiment? 2. Was the experiment able to illustrate a) The effect of changing concentrations of reactants/products b) The effect of temperature on equilibrium?
How so? *Be concise. You do not have to repeat the whole discussion to explain how your objectives were met or not met.
Answers:
1. The equilibria involved in the experiment is the (1) Iron-Silver Ion System ; (2) Copper-Ammonia Equilibrium; (3) Chromate-Dichromate Equilibrium ; (4) Iron Thiocyanate Equilibrium and (5) Cobalt Ion equilibrium. 2. (a) The effect of changing concentrations was illustrated by characteristic color changes which signify which formation is favoured.
(b) The effect of temperature is well-illustrated by the cobalt ion equilibrium which showed a change in color due to a favoured, endothermic reaction at the varied temperature.