A student investigates the formation of the complex ion \(\mathrm{FeSCN^{2+}}\) in aqueous solution at \(25^\circ\mathrm{C}\). The reaction is homogeneous (all species are dissolved):
A mixture is prepared by combining solutions to give initial concentrations (after mixing) of \([\mathrm{Fe^{3+}}]_0 = 0.100\ \mathrm{mol\ L^{-1}}\) and \([\mathrm{SCN^-}]_0 = 0.100\ \mathrm{mol\ L^{-1}}\) in a total volume of 1.00 L. After the system reaches equilibrium, a colorimeter measurement indicates that \([\mathrm{FeSCN^{2+}}]_{eq} = 2.00 \times 10^{-2}\ \mathrm{mol\ L^{-1}}\).
In a second trial, a separate equilibrium mixture is prepared at the same temperature with initial concentrations (after mixing) \([\mathrm{Fe^{3+}}]_0 = 0.0500\ \mathrm{mol\ L^{-1}}\) and \([\mathrm{SCN^-}]_0 = 0.200\ \mathrm{mol\ L^{-1}}\) in 1.00 L. No \(\mathrm{FeSCN^{2+}}\) is present initially.
Write the equilibrium constant expression \(K_{eq}\) for the reaction in terms of equilibrium concentrations.
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Create Free Account Log inThis is a free HSC HSC Chemistry practice question worth 2 marks, testing your understanding of Deduce the equilibrium expression (in terms. It falls under Calculating the Equilibrium Constant (Keq) in Module 5: Module 5: Equilibrium and Acid Reactions. Submit your answer above to receive instant AI-powered marking and personalised feedback.
Chemical systems may be open or closed. They include physical changes and chemical reactions that can result in observable changes to a system. Students study the effects of changes in temperature, concentration of chemicals and pressure on equilibrium systems, and consider that these can be predicted by applying Le Chatelier’s principle. Students also analyse the quantitative relationship between products and reactants in equilibrium reactions to determine an equilibrium constant. From this calculation, they predict the equilibrium position, either favouring the formation of products or reactants in a chemical reaction. This module also allows students to understand that scientific knowledge enables scientists to offer valid explanations and make reliable predictions. Students make reliable predictions by comparing equilibrium calculations and equilibrium constants to determine whether a combination of two solutions will result in the formation of a precipitate.
Inquiry question: How can the position of equilibrium be described and what does the equilibrium constant represent?
deduce the equilibrium expression (in terms of Keq) for homogeneous reactions occurring in solution (ACSCH079, ACSCH096)
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