Question

How can you separate alumina from silica in a bauxite ore associated with silica ?give equation, if any

Answer 1

Al2O3.2H2O+2NaOH->2NaAlO2+3H20 Bauxite dissolves and forms sodium aluminate leaving behind insoluble impurities called red mud which are removed by filtration. On diluting sodium aluminate with water and cooling to 50°C it gets hydrolysed to give Aluminum hydroxide as precipitate. The precipitate is filtered, washed, dried and ignited at 1000°C to get alumina. If you need further equations I can add them as comments.