(b) If a solution of Sn2+ ions were added to a blue solution of the [Co(H2O)6]2+
ID: 1027336 • Letter: #
Question
(b) If a solution of Sn2+ ions were added to a blue solution of the [Co(H2O)6]2+/[CoClf-equilibrium what would you observe? Justify your answer with balanced chemical equations and a discussion of Le Châtelier's principle. 4. When discussing the equilibrium constant expression, we have been writing the expression in terms of the concentrations of the gases, or aqueous species, in question. When dealing with gases, however, we can replace these molar concentrations with the partial pressures of the species. Using the ideal gas law (PV = nRT), show that the equilibrium constant expression for the Haber process expressed in terms of pressures is equal (to within a small constant factor) to the K expressed in terms of molarities. What is this factor? Show all work.Explanation / Answer
b) The equilibrium reaction is given as
[Co(H2O)6]2+ (aq) + 4 Cl- <=======> [CoCl4]2- (aq) + 6 H2O (l)
(pink) (blue)
K = [CoCl42-]/[Co(H2O)62+][Cl-]4
Sn2+ reacts with Cl- to form SnCl2. Therefore, when Sn2+ is added to [Co(H2O)6]2+/[CoCl4]2- equilibrium, the [Cl-] is reduced due to complexation with Sn2+. Consequently, the denominator in the expression for K decreases. However, K is an equilibrium constant and hence, must remain constant at a particular temperature. Therefore, to keep K constant, the numerator in the expression must decrease proportionately. This is possible only when the backward reaction is favored, i.e, [CoCl4]2- decomposes to produce more [Co(H2O)6]2+ and Cl-. Therefore, the pink color of the solution intensifies.
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