Temporary hardness of water is due to the presence of:

What is heavy water? Give its uses.

Given below are two statements: One is labelled as Assertion $A$ and the other labelled as Reason $R$.
Assertion $A$: During the boiling of water having temporary hardness,$Mg(HCO_3)_2$ is converted to $MgCO_3$.
Reason $R$: The solubility product of $Mg(OH)_2$ is greater than that of $MgCO_3$.
In the light of the above statements,choose the most appropriate answer from the options given below.

Which salt does not cause hardness in water?

An inorganic salt $(A)$ is decomposed on heating to give two products $(B)$ and $(C)$. Compound $(C)$ is a liquid at room temperature and is neutral to litmus,while the compound $(B)$ is a colourless neutral gas. Compounds $(A)$,$(B)$ and $(C)$ are:

The degree of hardness of water is usually expressed in terms of which of the following?