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)`.
What are the impurities present in bauxite ore?

Explanation

Silica, iron oxide and titanium oxide are the impurities present in bauxite.