CAIE A-Level Chemistry AS 7 Equilibria Questions

Define Le Chatelier's principle.

Reaction 1 describes the reversible reaction between yellow $\mathrm{Fe}^{3+}(\mathrm{aq})$ and colourless $\mathrm{SCN}^{-}(\mathrm{aq})$ to produce red $\mathrm{FeSCN}^{2+}(\mathrm{aq})$.
reaction 1

A mixture of $\mathrm{Fe}^{3+}(\mathrm{aq}), \mathrm{SCN}^{-}(\mathrm{aq})$ and $\mathrm{FeSCN}^{2+}(\mathrm{aq})$ is at equilibrium at $20^{\circ} \mathrm{C}$.
The temperature of this mixture is then increased to $50^{\circ} \mathrm{C}$ and allowed to reach equilibrium.
Deduce the changes that occur, if any, in the equilibrium mixture at $50^{\circ} \mathrm{C}$ compared to the equilibrium mixture at $20^{\circ} \mathrm{C}$.
- change in appearance
- change in relative concentration of $\mathrm{FeSCN}^{2+}(\mathrm{aq})$
- change in value of the equilibrium constant, $K_{\mathrm{c}}$

In another experiment, equimolar amounts of $\mathrm{Fe}^{3+}(\mathrm{aq})$ and $\mathrm{SCN}^{-}(\mathrm{aq})$ are mixed together and allowed to reach equilibrium. The total volume of the mixture is $25.0 \mathrm{~cm}^{3}$.
reaction $1 \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{SCN}^{-}(\mathrm{aq}) \rightleftharpoons \mathrm{FeSCN}^{2+}(\mathrm{aq})$
At equilibrium the mixture contains:
- $\left[\mathrm{SCN}^{-}\right]=1.30 \times 10^{-3} \mathrm{moldm}^{-3}$
- $\left[\mathrm{FeSCN}^{2+}\right]=0.300 \times 10^{-3} \mathrm{moldm}^{-3}$.