Temporary hardness in water is due to which one of the following of Calcium and Magnesium ?

Water hardness is classified into temporary and permanent types based on the dissolved salts of calcium and magnesium. Temporary hardness is specifically caused by the presence of dissolved calcium hydrogencarbonate (Ca(HCO3)2) and magnesium hydrogencarbonate (Mg(HCO3)2), also commonly referred to as bicarbonates [2]. This type of hardness is termed 'temporary' because it can be easily removed by boiling the water [2]. During boiling, these soluble hydrogencarbonates decompose into insoluble carbonates (like CaCO3) or hydroxides (like Mg(OH)2), which precipitate out as scale, thereby softening the water [2]. In contrast, permanent hardness is caused by the chlorides and sulphates of calcium and magnesium, which remain soluble even after boiling and require chemical treatment for removal [2].

Sources

1. [2] https://www.uptti.ac.in/classroom-content/data/Unit-1_Water%20and%20its%20treatment.pdf
2. [1] https://www.sciencedirect.com/topics/engineering/carbonate-hardness