Question

PART D: Study of the Equilibrium: Fe3+(aq) + SCN–

(aq) ⇌ [FeSCN]
2+(aq)
pale yellow red
20. Which reagent(s) did you use to enhance the formation of [FeSCN]

2+(aq)? Why?

21. Indicate which ion was added to or removed from the equilibrium mixture, based on the reagent(s)
you chose in question 20.

22. Which reagent(s) did you use to enhance the formation of Fe3+(aq)? Why?

23. Indicate which ion was added to or removed from the equilibrium mixture, based on the reagent(s)
you chose in question 22.

_____ 24. Upon heating in which direction is the equilibrium shifting? (L) left (R) right
_____ 25. Upon cooling in which direction is the equilibrium shifting? (L) left (R) right
_____ 26. Is the forward reaction A. endothermic B. exothermic
27. Explain your answers to questions 24, 25, and 26.

Answer 1

The reaction is

We can enhance the formation of [FeSCN]⁺² by increasing the concentration of reactants in the reaction. This is with respect to Le chatelier's principle. Le chatelier's principle states that if an equilibrium is disturbed by changing the conditions like concentration, pressure, volume etc, the position of equilibrium shifts to counteract the change in order to re-establish the equilibrium. If we increase the concentration of reactants, the equilibrium will shift to forward direction in order to re-establish the equilibrium thus enhancing the formation of [FeSCN]⁺² . The reagents used can be Fe(NO₃)₃ or K(SCN).

21. Fe⁺³ was added from Fe(NO₃)₃ and SCN^- was added from K(SCN) in order to enhance the formation of the product.

22. If there is less formation of [FeSCN]⁺² then the equilibrium will shift towards the left side as more reactants are formed. In order to do so, we can use AgNO₃ and K₃PO₄ as reagents. In the case of AgNO₃, the Ag⁺ forms precipitate with SCN^- thus there is no SCN^- left for the formation of [FeSCN]⁺² . This shifts the equilibrium to the left.

23. SCN^- was removed in case of AgNO₃.

24. Upon heating that is increasing the temperature, the equilibrium shifts to the left as more reactants are formed.

25. Upon cooling, the equilibrium shifts to the right as fewer products are formed.

26. In the forward reaction, [FeSCN]⁺² is formed that is bonds are formed between SCN^- and Fe⁺³. We know that energy is released when bonds are formed that is the forward reaction must be exothermic.

27. The explanations are provided within each part.

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