Answer: Ca(HCO 3 ) 2 and Mg(HCO 3 ) 2.
- A Ca(HCO<sub>3</sub>)<sub>2</sub> and Mg(HCO<sub>3</sub>)<sub>2</sub>
- B CaSO<sub>4</sub> and MgSO<sub>4</sub> as generally observed
- C CaCl<sub>2</sub> and MgCl<sub>2</sub> in typical laboratory settings
- D NaCl under usual circumstances
Correct answer: A. Ca(HCO<sub>3</sub>)<sub>2</sub> and Mg(HCO<sub>3</sub>)<sub>2</sub>
Explanation: Temporary hardness is caused by bicarbonates of calcium and magnesium, which can be removed by boiling.
Each water molecule's O-H bonds (covalent, solid) can hydrogen-bond (dashed) to neighbouring molecules, forming an extended network responsible for water's unusually high boiling point and density anomaly.
Concept context
The simplest and most abundant element in the universe. Study its unique position in the periodic table, isotopes (protium, deuterium, tritium), properties of water and hydrogen peroxide, and industrial uses.