Which of the following substances cause temporary hardness in water? 1. Mg(HC03)2 2. Ca(HC03)2 3. CaCl2 4. MgS04 Select the correct answer using the code given below.

Water hardness is categorized into temporary and permanent types based on the dissolved mineral salts. Temporary hardness, also known as carbonate hardness, is primarily caused by the presence of dissolved bicarbonates of calcium and magnesium, specifically Ca(HCO3)2 and Mg(HCO3)2. This type of hardness is termed 'temporary' because it can be easily removed by boiling the water, which causes the soluble bicarbonates to decompose into insoluble carbonates that precipitate out. In contrast, permanent hardness is caused by the presence of chlorides and sulphates of calcium and magnesium, such as CaCl2 and MgSO4. These salts are more stable and cannot be removed by simple boiling, requiring chemical treatment for removal. Therefore, substances 1 and 2 cause temporary hardness, while 3 and 4 cause permanent hardness.

Sources

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