Question

What happens when $SiO_2$ reacts with NaOH?
A- Sodium silicate if formed
B- Glass is formed
C- $Na_4 Si$ is formed
D- Does not give any reaction

Answer 1

Hint : Try to figure out how other members of the group react with NaOH. It is almost similar to the reaction of other elements of the group. This reaction is used to remove silica impurities from ores.

Complete step by step solution :
We know that silica has many applications. It is used in manufacturing glass, foundries, ceramics. Silica sand is used in water filtration and agriculture. Silica is present as an impurity in many ores.
Silica is not much soluble in acidic solution. Silica is slightly acidic so it reacts with strong bases like NaOH and KOH. This reaction is used in furnaces to purify ores of other metals in which silica impurity is present. Silica reacts with NaOH at very high temperatures around $900^0 C$ to form sodium silicate slag. The reaction will be:

$2NaOH\quad +\quad SiO_{ 2 }\quad →\quad Na_{ 2 }SiO_{ 3 }\quad +\quad H_{ 2 }O$

This reaction is used in many places for the removal of silica impurities. This slag floats on the surface of the ore and thus can easily be separated from purified ore.
So, the correct answer is “Option A”.

Note : Sodium hydroxide reacts with silica concrete, silica glass, and damages them. Silicates also polymerize in basic conditions. Silica reacts with alkali in the presence of moisture resulting in the formation of an alkali-silica gel. This gel has many uses. Carbon dioxide which is the same group oxide reacts with alkali similarly.