Deep sea divers have been using the compressed air containing \({ N }_{ 2 }\) in addition to \({ O }_{ 2 }\) for breathing. When the sea diver breathes in compressed air at a depth, more \({ N }_{ 2 }\) dissolves in the blood and other body fluids than would dissolve at the surface because the pressure at the depth is far greater than surface atmospheric pressure. When the diver comes towards the surface, the pressure decreases and  \({ N }_{ 2 }\) comes out of the body quickly forming bubbles in the blood stream which restrict blood flow and affect the transmission of nerve impulses. This results into a condition called 'the bends' which is dangerous and painful. To avoid this condition, professionals now use air diluted with helium. As a student of chemistry, can you analyse as to why helium is used?

Common salt \((NaCI)\) and calcium chloride \((CaCI_{ 2 })\) are used to clear snow on the roads. The cost of sodium chloride and calcium chloride is almost the same. As a student of chemistry which salt would you prefer to purchase and why?

Jagan went to Srinagar with his friend. He noticed that the taxi drivers always add ethylene glycol as a coolant in the radiator of the taxi and not water. He asked his driver, how much ethylene glycol he generally adds to the radiator. The taxi driver told him that he generally adds 30% ethylene glycol solution. On that day, the temperature of the valley was \(-10°C\) .
Answer the following questions:
(i) What is the role ethylene glycol when added to water?
(ii) Is the amount of ethylene glycol sufficient to avoid the freezing of water in car radiator when the temperature of the valley was \(-10°C\) ?

Rekha observed that her mother placed shrinked or dried vegetables in water before cutting these for cooking. After sometime, these vegetables looked fresh.
Answer the following questions:
(i) Why did Rekha's mother place the shrinked or dried vegetables in water?
(ii) What is the name of the process used and define it.
(iii) Would the temperature increase accelerate the process or not?