Types of hardness of water is: (A)temporary and semi-permanent (B)permanent and temporary (C)permanent and partially permanent (D)none of the above
Hint: Hardness is due to the presence of salts of chlorides and sulphides, also, caused by formation of insoluble salts of carbonates. Some hardness can be removed by a simple process, others required, specific treatment to be used.
Complete answer: Water is the most essential compound for survival of life on earth.Rainwater is considered as the purest form of water because it does not contain any dissolved salt in it, although it has some dissolved gases. Water can be grouped as Soft water and Hard water. Soft water: It gives lather with soap.Rainwater is soft water. This water is acceptable for household purposes, for laundries and cleaning purposes. Hard water: It does not give lather with soap. Instead of forming lather, it forms precipitate. Hardness of water is due to presence of soluble chlorides, bicarbonates, and sulfates of calcium and magnesium. Water which does not give lather after mixing soap is Hard water. Hard water is not suitable for use in boilers, as they leave deposition of salts in the container which affects the efficiency of the boilers. Hardness of water can be classified in two types: 1)Temporary hardness 2)Permanent hardness Temporary hardness is due to the presence of magnesium and calcium carbonates in the water. On boiling, these salts get converted into magnesium and calcium hydroxides which are insoluble and get precipitated, and can be separated out by filtration. Therefore, temporary hardness can be removed by boiling. Permanent hardness is due to the presence of magnesium and calcium are present in the form of sulphates and chlorides salts in water. We cannot remove them by boiling, thus, it is called permanent hardness. Permanent hardness can be removed by treating the water with washing soda. On reaction with washing soda , insoluble salts of carbonates are formed, from chlorides and sulphides salts of magnesium and calcium. This is how hard water is converted into soft water.
Therefore, the correct answer is (B) option.
Note: Hardness of water results in wastage of soap, wastage of fuel and formation of scales on the metallic boilers. Hair wash done with hard water, looks sticky dull, due to deposition of salts.