An aqueous solution at 25 °C contains the equilibrium Fe (aq) + SCN (aq) ⇌ FeSCN (aq)…
CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
An aqueous solution at 25 °C contains the equilibrium
Fe3+(aq) + SCN−(aq) ⇌ FeSCN2+(aq) (red)
Distilled water is added, doubling the total volume and keeping temperature constant. Which statement best describes the change observed as the system reaches a new equilibrium?
(a) The equilibrium shifts right and the red color intensifies.
(b) There is no shift because water is a pure liquid and not included in the equilibrium expression.
(c) The equilibrium shifts left and the red color fades.
(d) The value of K decreases because dilution favors the reverse reaction.