Question

$Si{O_2}$ is reacted with sodium carbonate. What is the gas liberated?
A) $CO$
B) $O_2$
C) $CO_2$
D) $O_3$

Answer 1

When silica is heated with metal carbonate, it forms ortho-silicate and the sodium carbonate will undergo decomposition in the presence of acidic oxide.

Complete answer:
Sodium carbonate is more commonly known as washing soda. Like the similar-sounding compound sodium bicarbonate—baking soda—it's basic and can react with acids. $HCl,$ or hydrochloric acid, is a strong acid that reacts with sodium carbonate. The reaction produces large quantities of carbon dioxide gas, water, and table salt.
When you mix sodium carbonate and $HCl,$ two molecules of $HCl,$ give their hydrogen atoms to the sodium carbonate. This produces carbonic acid, with the formula ${H_2}C{O_3}.$
Likewise, when silica $\left( {acidic{\text{ }}oxide} \right)$ is mixed with solid sodium carbonate and melted, sodium silicate is formed. This reaction is the basic reaction in the manufacture of glass.

${SiO_2} + {Na_2CO_3} \to {Na_2SiO_3} + {CO_2}$
Hence we can see from the reaction Carbon-dioxide is released.

Therefore, the correct answer is C).

Note: Sodium silicate can be hardened in some ways by adding weak acids or by adding various silicate powders or by removing water. Gas and liquid ester are the most widely used in the silicate process of hardening.