When zeolite is treated with hard water,the sodium ions are exchanged with:

When the first element of the periodic table is treated with dioxygen,it gives a compound whose solid state floats on its liquid state. This compound has an ability to act as an acid as well as a base. What products will be formed when this compound undergoes autoionisation?

The $O-H$ bond length in $H_2O$ in the gas phase is: (in $pm$)

Amongst the following,the form of water with the lowest ionic conductance at $298 \ K$ is

Exhausted permutit is

Temporary hardness of water is due to the presence of: