Question

Which compound is used as an antacid?
(A) Soda ash
(B) Baking soda
(C) Nitrous oxide
(D) Magnesium carbonate

Answer 1

Antacids are a category of drugs which are used for the treatment of acidity in the stomach. Antacids are substances which can neutralize the excess acid in the stomach and raise the pH to a suitable level in the stomach. Generally, bases are used as antacids.

Complete step by step answer: When excessive amounts of acids are formed in the stomach, i.e., when there is overproduction of acids in the stomach, it causes irritation as well as pain. In extreme cases, ulcers are formed in the stomach. Since acids are neutralized by bases, therefore the most commonly used antacids are bases like aluminium hydroxide gel, magnesium hydroxide, magnesium carbonate, sodium bicarbonate, aluminium phosphate etc.
Now, let us check the given options one by one.
Soda ash is another name for sodium carbonate. It has the chemical formula ${\text{N}}{{\text{a}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}$ . It forms sodium hydroxide when dissolved in water. It is commonly known as washing soda and is quite alkaline and has a soapy taste. Thus, it is not edible and cannot be used as an antacid. So option A is not correct.
Baking soda is another name for sodium bicarbonate or sodium hydrogen carbonate. It has the chemical formula ${\text{NaHC}}{{\text{O}}_{\text{3}}}$ . It is alkaline in nature and hence can be used to treat acid indigestion and heartburns. When it reacts with stomach acid, salt, water and carbon dioxide is produced. The reaction is shown below:
${\text{NaHC}}{{\text{O}}_{\text{3}}}{\text{ + HCl}} \to {\text{NaCl + }}{{\text{H}}_{\text{2}}}{\text{O + C}}{{\text{O}}_{\text{2}}}$

Hence, option B is correct.

Nitrous oxide $\left( {{{\text{N}}_{\text{2}}}{\text{O}}} \right)$ is a neutral oxide which means it can display neither acidic properties nor basic properties. Therefore it cannot neutralize acids and hence is not used as an antacid. So, option C is not correct.
Magnesium carbonate $\left( {{\text{MgC}}{{\text{O}}_{\text{3}}}} \right)$ is basic in nature and hence, it can neutralize acids to form salt, carbon dioxide and water.
${\text{MgC}}{{\text{O}}_{\text{3}}}{\text{ + 2HCl}} \to {\text{MgC}}{{\text{l}}_{\text{2}}}{\text{ + C}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$

So it can also be used as an antacid. So, option D is also correct.

Note: Excessive bicarbonate can make the stomach highly alkaline and this can trigger the production of acid in the stomach even more. Thus, metal hydroxides are considered to be better alternatives than bicarbonates as antacids because the metal hydroxides are insoluble and do not raise the pH level above neutrality.