Define Le Chatelier's principle.

1. (a)Define Le Chatelier's principle.[2]
2. (b)Reaction 1 describes the reversible reaction between yellow Fe3+(aq) and colourless SCN-(aq) to produce red FeSCN2+(aq). reaction 1 Fe3+(aq) + SCN-(aq) ⇋ FeSCN2+(aq) ΔH = -x kJ mol-1 yellow colourless red A mixture of Fe3+(aq), SCN-(aq) and FeSCN2+(aq) is at equilibrium at 20°C. The temperature of this mixture is then increased to 50 °C and allowed to reach equilibrium. Deduce the changes that occur, if any, in the equilibrium mixture at 50°C compared to the equilibrium mixture at 20 °C. • change in appearance • change in relative concentration of FeSCN2+(aq) • change in value of the equilibrium constant, Kc[3]
3. (c)In another experiment, equimolar amounts of Fe3+(aq) and SCN¯(aq) are mixed together and allowed to reach equilibrium. The total volume of the mixture is 25.0cm³. reaction 1 Fe3+(aq) + SCN-(aq) ⇋ FeSCN2+(aq) At equilibrium the mixture contains: • [SCN¯] = 1.30 × 10-3moldm−3 • [FeSCN2+] = 0.300 × 10−3moldm−3.
4. (c)(i)Calculate the initial amount, in mol, of Fe3+(aq) added to SCN-(aq) to produce this mixture. initial amount of Fe3+(aq) = .............................................. mol[2]
5. (c)(ii)Calculate Kc for reaction 1 and state its units. Show your working. Kc = .............................................. units ..............................................[2]