Which of the statements given below is/ are correct ? Permanent hardness of water is due to the presence of soluble : 1. chloride of calcium. 2. bicarbonate of calcium. 3. sulphate of magnesium. 4. bicarbonate of magnesium. Select the correct answer using the code given below :

Water hardness is classified into temporary and permanent types based on the dissolved salts present. Temporary hardness is caused by the presence of dissolved bicarbonates of calcium and magnesium, which can be removed by boiling [t2, t4, t10]. In contrast, permanent hardness (also known as non-carbonate hardness) is caused by the presence of dissolved chlorides and sulphates of calcium and magnesium [t2, t6, t8]. Specifically, salts such as calcium chloride (CaCl2) and magnesium sulphate (MgSO4) are responsible for permanent hardness because they cannot be removed by simple boiling and require chemical treatment for removal [t2, t7, t10]. Therefore, statement 1 (chloride of calcium) and statement 3 (sulphate of magnesium) are correct, while statements 2 and 4 refer to temporary hardness.

Sources

1. [1] https://uptti.ac.in/classroom-content/data/Unit-1_Water%20and%20its%20treatment.pdf
2. [2] https://www.griet.ac.in/nodes/EC_UNIT_1.pdf