Which of the following substances cause temporary hardness in water? 1. Mg(HCO3)2 2. Ca(HCO3)2 3. CaCl2 4. MgSO4

There are two types of water hardness: temporary and permanent hardness. Temporary hardness is due to the presence of calcium hydrogen carbonate Ca(HCO3)2(aq) and magnesium hydrogen carbonate Mg(HCO3)2(aq).