Write the equilibrium expression for the reaction between Fe^3t and SCN: Fe^3+ (
ID: 507354 • Letter: W
Question
Write the equilibrium expression for the reaction between Fe^3t and SCN: Fe^3+ (aq) + SCN' (aq) doubleheadarrow FeSCN^2+ (aq) Given the following equations, explain the results you obtained for Part One. FeSCN^2+ (aq) + Ag^+ (aq) doubleheadarrow AgSCN (s) + Fe^3+ (aq) FeSCN^2+ (aq) + F (aq) doubleheadarrow FeF^2+ (aq) + SCN (aq) If a reaction is exothermic, adding heat will shift the equilibrium to the left (towards the reactants) and removing heat will shift the equilibrium to the right (towards the products). The opposite holds true for endothermic reactions. Based upon your results, classify each of the reaction systems you studied in Part Two as exothermic or endothermic. Consider the following endothermic catalytic decomposition of hydrogen sulfide: 2 H_2S(g) doubleheadarrow 2 H_2 (g) S_2(g) The reaction is performed in a metal cylinder fitted with a piston. Predict the direction in which the equilibrium shifts for the following changes: Addition of H_2 gas Increase in temperature Addition of liquid H_2S Compression of the piston and thus decreasing the reaction volumeExplanation / Answer
1 a) The given reaction is
Fe3+ (aq) + SCN- (aq) <-------> FeSCN2+ (aq)
The equilibrium constant is given by
K = [FeSCN2+]/[Fe3+][SCN-] …..(1)
b) The given reaction is
FeSCN2+ (aq) + Ag+ (aq) <------> AgSCN (s) + Fe3+ (aq)
The above reaction consumes FeSCN2+ and produces Fe3+. Therefore, the numerator of expression (1) in (a) decreases while the denominator decreases. However, K is constant at a particular temperature. Hence, to keep K constant, the reaction in (a) must shift to the right, i.e, the equilibrium shifts to the right. Hence, the equation in (b) leads to formation of more product in (a).
The reaction is
FeSCN2+ (aq) + F- (aq) <------> FeF2+ (aq) + SCN- (aq)
The above reaction consumes FeSCN2+ and produces more SCN-. The numerator in expression (1) decreases while the denominator increases. To keep K constant, therefore, the reaction in (a) must produce more FeSCN2+. Therefore, the equilibrium shifts to the right.
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