Question

In the leaching of Alumina from bauxite, concentration of the ore is done by digesting the powdered ore with $NaOH$ and then it is later reacted with $C{O}_2$ gas. Consider the major impurities presents related to them.

I. $Si{O}_2$ is leached out along with $A{l}_2{O}_3$ as silicate and aluminate on reaction with $NaOH$.

II. Iron oxides and titanium oxide are insoluble in $NaOH$ and are left behind as impurity.

III. On passing $C{O}_2$, the silicate is precipitated leaving aluminate in the filtate from which Alumina can be recovered.

The correct statements from the ones given are

• A. II and III only
• B. I and II only
• C. I and III only
• D. I, II and III

Answer 1

The correct option is B I and II only

$A{l}_2{O}_3,Si{O}_2,Ti{O}_2$ and Iron oxides
$\downarrow NaOH$

$A{l}_2{O}_3$ and $Si{O}_2$, dissolve as aluminate and silicate $\downarrow C{O}_2$

$A{l}_2{O}_3$, precipitates + Silicate remaining in solution.