Lime or $CaCl_2$ is added to water to remove which of the following impurities?

Provide general information about water $(H_2O)$.

Which of the following statements is/are correct?

Which of the following methods is used to remove hardness from water?

Which of the following compounds liberates an acidic gas during its hydrolysis?

Some statements about heavy water are given below:
$(i)$ Heavy water is used as a moderator in nuclear reactors.
$(ii)$ Heavy water is more associated than ordinary water.
$(iii)$ Heavy water is more effective solvent than ordinary water.
Which of the above statements are correct?