Why does effervescence occur when acid is added to sodium hydrogen carbonate?
Answer and explanation
Correct answer: Carbon dioxide gas is released
The governing concept is the acid–carbonate reaction. When an acid reacts with sodium hydrogen carbonate, the products are a salt, water and carbon dioxide: acid + NaHCO₃ → salt + H₂O + CO₂. The escaping carbon dioxide forms visible bubbles, producing effervescence. Hydrogen is not released, salt vapour is not formed, and freezing water cannot explain the observation. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
Carbon dioxide gas is released
Why is this the correct answer?
The governing concept is the acid–carbonate reaction. When an acid reacts with sodium hydrogen carbonate, the products are a salt, water and carbon dioxide: acid + NaHCO₃ → salt + H₂O + CO₂. The escaping carbon dioxide forms visible bubbles, producing effervescence. Hydrogen is not released, salt vapour is not formed, and freezing water cannot explain the observation. Therefore option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
