(a) The three properties are:-
(i) The reaction occurring in the system is reversible.
(ii) the rate of the forward reaction is equal to that of the reverse reaction
(iii) The value of the free energy change of the system is zero

(b)(i) Since the forward reaction is exothermic, increase in temperature will not favour the forward reaction. The yield of ammonia will be lower.

(c)(i) The ore is powdered and dissolved under pressure in a hot concentrated solution of sodium hydroxide. Sodium aluminate solution is formed Al${}_2$O${}_3$ + 2NaOH $\to$ 2NaAIO${}_2$ + H${}_2$O. The impurities do not dissolve and filtered off. The sodium aluminium hydroxide to precipitate the hydroxide which is filtered off, washed, dried and heated strongly to form pure alumina.
2A1(OH)${}_3$ $\to$ Al${}_2$O${}_3$ + 3H${}_2$O
Al${}_2$O${}_{3(s)}$ + 2NaOH${}_{(aq)}$ + 3H${}_2$O --> 2NaAl(OH)${}_4$
Then; NaAI(OH)${}_{4(aq)}$ --> Al(OH)${}_{3(s)}$ + NaOH${}_{(aq)}$
(ii) At the ANODE: 2O${}^{2-}$ - 4e${}^{-}$ $\to$ O${}_2$ OR 2O${}^{2-}$ ---> O${}_2$ + 4e${}^{-}$
At the CATHODE: Al${}^{3+}$ + 3e${}^{-}$ -> Al
(iii) The function is to act as a solvent or as a flux.