For the aqueous equilibrium five separate actions are carried out on identical…

CHEMISTRY · Subjective · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

For the aqueous equilibrium Fe3+(aq)+SCN−(aq)  ⇌  FeSCN2+(aq)(ΔH<0)\mathrm{Fe^{3+}(aq)+SCN^{-}(aq)\;\rightleftharpoons\;FeSCN^{2+}(aq)}\qquad (\Delta H<0) five separate actions are carried out on identical equilibrium mixtures. A. Add 1.0 mL\mathrm{1.0\,mL} of 0.10 M Fe(NO3)3\mathrm{0.10\,M\,Fe(NO_3)_3}. B. Add 1.0 mL\mathrm{1.0\,mL} of 0.10 M KSCN\mathrm{0.10\,M\,KSCN}. C. Add 5.0 mL\mathrm{5.0\,mL} of distilled water. D. Cool the solution from 25 ∘ ⁣C25\,^{\circ}\!\mathrm{C} to 20 ∘ ⁣C20\,^{\circ}\!\mathrm{C}. E. Add a few crystals of an inert salt KNO3\mathrm{KNO_3} (negligible volume change). Rank the actions from greatest to least predicted increase in the equilibrium concentration of FeSCN2+\mathrm{FeSCN^{2+}}. Ties should be grouped.

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