In a beaker, the reaction mixture is at equilibrium with the following…

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

Problem

In a beaker, the reaction mixture

\mathrm{Fe^{3+}(aq) + SCN^-(aq) \rightleftharpoons FeSCN^{2+}(aq)}

is at equilibrium with the following concentrations:

[\mathrm{Fe^{3+}}]=0.010\,\text{M}

[\mathrm{SCN^-}]=0.010\,\text{M}

, and

[\mathrm{FeSCN^{2+}}]=0.0010\,\text{M}

. The mixture is then quickly diluted by adding an equal volume of pure water, and temperature is kept constant. Which prediction about the system right after dilution is most accurate? (a) The equilibrium constant decreases, causing the system to shift toward the reactants. (b) Because all species are diluted equally, the value of

Q

remains equal to

K

, so the position of equilibrium is unchanged. (c) The reaction quotient

Q

becomes greater than

K

, so

\mathrm{FeSCN^{2+}}

dissociates until equilibrium is re-established. (d) The reaction quotient

Q

becomes less than

K

, so more

\mathrm{FeSCN^{2+}}

forms until equilibrium is re-established.

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