Question

A compound ‘X’ of sodium is used as an antacid and it decomposes on strong heating.
(i) Name the compound ‘X’ and give its chemical formula.
(ii) Write a balanced chemical equation to represent the decomposition of ‘X’.
(iii) Give one use of compound ‘X’ beside an antacid.

Answer 1

Hint: The compound is commonly known as baking soda. It is basic in nature and is also used to relieve heartburn and acid indigestion. It is a salt of carbonic acid.

Complete answer:
The compound which is frequently used in antacids is sodium bicarbonate. It is a white crystalline solid made up of sodium cation and bicarbonate anion. Its chemical formula is - $\text{NaHC}{\text{O}}_3$.
On heating strongly, sodium bicarbonate decomposes to produce sodium carbonate, carbon dioxide, and water. The reaction can be written as follows:
$$\begin{array}{rl}& 2\text{NaHC}{\text{O}}_3\stackrel{\mathrm{\Delta }}{\to }\text{N}{\text{a}}_2\text{C}{\text{O}}_3+{\text{H}}_2\text{O}+\text{C}{\text{O}}_2\\ & \text{Sodium bicarbonate}\stackrel{\mathrm{\Delta }}{\to }\text{Sodium carbonate}+\text{Water}+\text{Carbon dioxide}\end{array}$$
This reaction is used as the principal basis in the working of fire extinguishers, and its use as baking soda. When it is exposed to heat or fire, it decomposes to form carbon dioxide which extinguishes the fire. And it is used in baking because carbon dioxide is produced when heat is provided to the food and the release of carbon dioxide produces effervescence. And this causes the dough to rise.
It is also used as an antacid as it reacts with excess acid produced in the stomach and neutralizes it by producing sodium chloride salt and water. The reaction involved is shown below:
$$\text{NaHC}{\text{O}}_3+\text{HCl}\to \text{NaCl}+{\text{H}}_2\text{O}+\text{C}{\text{O}}_2$$
Hence, the correct answers are –
(i) Compound ‘X’ is Sodium bicarbonate. Its chemical formula is $\text{NaHC}{\text{O}}_{\text{3}}$.
(ii) Decomposition reaction of ‘X’:
$$2\text{NaHC}{\text{O}}_3\stackrel{\mathrm{\Delta }}{\to }\text{N}{\text{a}}_2\text{C}{\text{O}}_3+{\text{H}}_2\text{O}+\text{C}{\text{O}}_2$$
(iii) Besides the use of antacid, it is also used in fire extinguishers.

Note:
Sodium bicarbonate or baking soda is prepared by reacting a cold concentrated solution of NaCl with ammonia and carbon dioxide.
$$\text{NaCl}+\text{N}{\text{H}}_3+{\text{H}}_2\text{O}+\text{C}{\text{O}}_2\to \text{NaHC}{\text{O}}_3+\text{N}{\text{H}}_4\text{Cl}$$