Scientific Reasons

1. Baking powder is used in the preparation of spongy bread & cake.

Ans. i) Baking powder contains sodium bicarbonate (baking soda) & tartaric acid. In the reaction baking soda generates carbon dioxide gas.

ii) Due to CO₂ gas, bread & cakes are prepared using this swell & become light & fluffy. Hence   baking powder (NaHCO₃) is used in the preparation of spongy bread &cakes.

2. Sodium bicarbonate is used in fire extinguishers.

i) When sodium bicarbonate is treated with an acid carbon dioxide is formed.

ii CO₂ is neither combistible nor does it support combustion. It is heavier than air.

iii) It is used to extinguish fire. Hence sodium bicarbonate is used in fire extinguishers.

3. Bleaching powder is sold commercially on the basis of available chlorine.

Ans. i) Bleaching powder is also known as chloride of lime & the chlorine generated  is known    as available chlorine.

ii) The effectiveness of bleaching powder as disinfectant depends upon the chlorine content (available chlorine).

iii) The value of bleaching powder in the market is proportional to the quantity of available chlorine.

iv) Higher the chlorine content, higher is its price.

4. Bleaching powder must be stored in air-tight container.

Ans. i) Properties of bleaching powder are due to its chlorine content.

ii) If exposed to air bleaching powder reacts with atmospheric carbon dioxide, sets free chlorine & changes into ordinary chalk.

iii) Bleaching powder also reacts with moist air & releases chlorine.

iv) This decomposition can be minimized by storing bleaching powder in air-tight containers & using it before it gets decomposed.

5. Bleaching powder is often added to water in swimming pools or sprinkled on uncleared garbage.

Ans. i) Bleaching powder decomposes slowly on contact are moist air, water & atmosphere carbon          dioxide.

ii) Decomposition products are calcium carbonate & chlorine.

iii) Chlorine is excellent disinfectant, kills germs in water in the swimming pool.

iv) When sprayed on garbage, it discourages houseflies, cockroaches, etc; from sitting on it, besides killing the germs in it.

6. Antacids are used to cure indigestion.

Ans. i) Hydrochloric acid of p^H about 1.4, produced in the stomoch helps in the digestion of food.

ii) During indigestion, exess of acid is produced in the stomoch which causes pain & irritation.

iii) In order to cure indigestion, people use basic substances called antacids.

iv) There antacids neutralize the excess acid in the stomoch. Hence antacids are used to cure indigestion.