1.
An experiment to determine the equilibrium constant for the reaction between sodiurn fluonde solution
and magnesium hydroxide is carried out.
100 cm of sodium fluoride solution, of concentration 0.250 mol dm is added to a conical flask Excess
solid magnesium hydroxide is added and the mixture is left for 24 hours to reach equilibrium
The mixture is filtered and 25.0 cm
of the solution is removed and titrated with hydrochloric acid,
11.70 cm of 0.100 mol dm' HCl(aq) is required to neutralise the NaOH formed.

(b) Use the data to calculate the equilibrium constant, Kc for the reaction between NaF and Mg(OH)2
Give your answer to an appropriate number of significant figures and give the units, if any.
2NaF(aq) + Mg(OH)2(s) = 2NaOH(aq) + MgF2 (s)