Question

Answer the following:

(1) How do metal carbonates react with acids?

(2) Explain in detail about hydronium ion.

(3) What is universal indicator? Does Mg(OH)₂ react with sodium hydroxide? If not, why?

(4) State applications of baking soda.

Answer 1

(1) Reaction of metal carbonates with acid: When a metal carbonate or metal hydrogen carbonate reacts with an acid, it forms corresponding salt and liberates carbon dioxide gas.

(2) The strength of an acid is measured in terms of the extent of ionization of the acid in aqueous solution. It means more the acid ionizes more will be the strength of the acid.

Higher the H⁺ ions concentration stronger is the acid. Hydrogen ion (H⁺) is a highly reactive species so it does not exist in free state. Hence, once produced, hydrogen ion combines immediately with H₂O to form hydronium ion (H₃O⁺).

(3) Universal indicator: It is an indicator which is a mixture of several indicators. It has a wide range and it can indicate pH value almost from 0 to 14. Universal indicator is available as a solution or in the form of paper strips.

Mg(OH)₂ does not react with sodium hydroxide because both are bases.

(4) Baking soda is the white amorphous powdered soda. Its chemical name is sodium hydrogen carbonate or sodium bicarbonate and its formula is NaHCO₃. When tested with litmus, it turns red litmus blue, which indicates that it is alkaline in nature.

Sodium bicarbonate is extensively used in day−to−day life. Following are some of the applications of baking soda:

• It is used to prepare cakes and dhokla.

• Being alkaline, it also helps to reduce acidity in stomach.

• It is very useful in preparing CO₂ gas.

• It is one of the contents of fire extinguishers.