Q.Why are cimetidine and ranitidine better antacids than sodium hydrogencarbonate or magnesium or aluminium hydroxide ?

Antacids: What They Are and How They Work

Imagine you've just eaten a heavy, spicy meal. Your stomach works by releasing hydrochloric acid (HCl) to digest food. That acid is strong — strong enough to break down proteins. Normally, your stomach lining is protected. But sometimes, the acid gets too much: you feel a burning sensation in your chest or stomach. That's hyperacidity.

What do you want? Something that will neutralise that extra acid — turn it into harmless substances like water and salt. That's exactly what an antacid does.

The Chemistry in Simple Terms

Stomach acid is mostly hydrochloric acid, HCl. An antacid is typically a weak base — often a metal hydroxide or carbonate. The reaction is a simple acid-base neutralisation:

For example, magnesium hydroxide, $\ce{Mg(OH)2}$, reacts with HCl:

The acid is gone; the burning stops.

Common Antacids and Their Chemistry

Many commercial antacids combine magnesium and aluminium hydroxides to balance the side effects.

A Common Confusion: Ranitidine

You mentioned ranitidine. Here's the critical distinction: …