Solution 2: Aluminium contains silica 
, iron oxide 
and titanium oxide 
as impurities. These impurities can be removed by the process of leaching.
During leaching, the powdered bauxite ore is heated with a concentrated ( 
) solution of 
at 
, where alumina dissolves as sodium meta aluminate and silica as sodium silicate leaving 
and other impurities behind:
](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-1da8c05836df5a9c7a49a4afeafe2360_l3.png "Rendered by QuickLaTeX.com")
Sodium meta – aluminate
![\[\mathrm{SiO}_{2}(l)+2 \mathrm{NaOH}(a q) \stackrel{473-523 \mathrm{~K}}{\longrightarrow} \mathrm{Na}_{2} \mathrm{SiO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)\]](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-f154f5604f6ce71e8fade1d15a064580_l3.png "Rendered by QuickLaTeX.com")
Sodium silicate
The impurities are filtered off and solution of sodium meta-aluminate is neutralised by passing 
when hydrated alumina separates out while sodium silicate remains in solution. The hydrated alumina thus obtained is filtered, dried and heated to give back pure alumina. 
.
)
west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points above the horizontal. The horizontal component of the earth’s field is measured to be 
Specify the direction and magnitude of the earth’s field at the location.At a certain location in Africa, a compass points 
and 
carrying currents of 
and 
in the same direction are separated by a distance of 
. Estimate the force on a 
section of wire A.
wire carrying a current of 
is placed inside a solenoid perpendicular to its axis. The magnetic field inside the solenoid is given to be 
. What is the magnetic force on the wire?
and making an angle of 
with the direction of a uniform magnetic field of 
. What is the magnitude of the field 
at a point 
from the wire?
-turns carrying current 
.
is at distance 
from the wire. Find the force acting on the electron if its velocity is directed towards the wire.