Read the given passage and answer the questions number 1 to 5 that follow : Bauxite is the principal ore of aluminium. It usually contains SiO_(2), iron oxides and titanium oxide (TiO_2) as impurities. Concentration is carried out by heating the powdered ore with a concentrated solution of NaOH at 473-523 K and 35-36 bar pressure. This process is called digestion. This way, Al_(2)O_(3) is extracted out as sodium aluminate. The impurities, SiO_(2), too dissolves forming sodium silicate. Other impurities are left behind. Al_(2)O_(3)(s)+2NaOH(aq)+3H_(2)O(l) to 2Na[Al(OH)_(4)](aq) The sodium aluminate present in solution is neutralised by passing CO_2 gas and hydrated Al_(2)O_(3) is precipitated. At this stage, small amount of freshly prepared sample of hydrated Al_(2)O_(3) is added to the solution. This is called seeding. It induces the precipitation. 2Na[Al(OH)_(4)](aq)+CO_(2)(g) to Al_(2)O_(3).xH_(2)O(s)+2NaHCO_(3) (aq) Sodium silicate remains in the solution and hydrated alumina is filtered, dried and heated to give back pure Al_(2)O_(3). Al_(2)O_(3).xH_(2)O(s) overset(1470K)(to) Al_(2)O_(3)(s)+xH_(2)O(g). Give the reaction conditions in the digestion of bauxite with sodium hydroxide.