Test: Water (Old NCERT) - NEET MCQ

In redox reactions, water reacts with metals and nonmetals both. For example, take the reaction of sodium with water, the products are sodium hydroxide and hydrogen, whereas fluorine reacts with water in order to form hydrogen cation and fluorine anion with oxygen.

In hydrated salt, there are five types of water. The five types of water in hydrated salt are i. coordinated water, ii. hydrogen bonded water, iii. lattice water, iv. clathrate water and v. zeolite water.

Ice floats on water, this is because of the density of ice i.e. mass per unit volume (density of ice is 0.9167 g/cm³ and density of water is 1g/cm³) is lesser than that of water. This is the reason, ice floats over water.

The water which forms come with soap is known as hard water. The hardness that occurs due to the presence of bicarbonates of calcium and magnesium is temporary hardness. Temporary hardness can be removed by boiling and Clark’s process.

Permutit is hydrated sodium aluminum silicate, it exchanges it’s sodium ions for divalent ions of calcium and magnesium, permutit when fully exhausted can be regenerated by treating with 10% of sodium chloride solution. It is the most efficient method to get water with zero degrees of hardness.

The methods that are used for removing the temporary hardness of water are by boiling and by Clark’s process. Adding washing soda, caustic soda and sodium phosphates are for permanent hardness removal.

Permanent hardness is removed by Calgon process. In this process, Calgon is referred to Sodium hexametaphosphate and its chemical formula is given by Na₆P₆O₁₈. This Calgon when added to hard water forms soluble complex.

There are two types of synthetic resins used for removal of permanent hardness. They are cation exchange resins which are big molecules containing sulfonic acid group and an anion exchange resins which are also big molecules containing amino acids.

Water has a hybridization of sp³. In a water molecule oxygen has two lone pairs and two bonded hydrogens. Its structure is V in shape and has a bent structure. Water has a chemical formula of H₂O.

Water has a maximum density at 4-degree centigrade, this is because at 4-degree centigrade, as opposite forces are in balance that is like the formation of Ice and maintaining of the liquid phase of water. Any less than 4-degree centigrade or greater than 4-degree centigrade, the water density is lesser than that of 4-degree centigrade.