Effervescent tablets are composed of

• A. A mixture of citric, tartaric acids, and sodium bicarbonate
• B. Sodium chloride and citric acid
• C. Calcium carbonate and glucose
• D. Magnesium stearate and lactose

Answer: (A)

Effervescence comes from an acid–base reaction when the tablet is put in water, producing carbon dioxide. A proper effervescent formulation includes an acid (or acids) and a carbonate/bicarbonate salt that react to release CO2 and fizz, helping the tablet dissolve quickly. The classic combination uses citric acid and tartaric acids together with sodium bicarbonate, so this option matches the required acid–base pair for gas evolution. The other formulations miss the essential reacting component or rely on inert excipients: sodium chloride with citric acid lacks the bicarbonate; calcium carbonate and glucose don’t provide the right acid–base system for rapid CO2 release; magnesium stearate and lactose are just lubricants/fillers and don’t produce fizz.