Which of the following is the best scientific method to test the presence of water in a liquid?

Discuss the principle and method of softening of hard water by synthetic ion-exchange.

Plumbosolvency is a health hazard in the transportation of

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 ratio of the viscosity (in centipoise) of $D_2O$ to that of $H_2O$ at $25^{\circ} C$ is

The reagent$(s)$ used for softening the temporary hardness of water is(are):
$(A)$ $Ca_3(PO_4)_2$
$(B)$ $Ca(OH)_2$
$(C)$ $Na_2CO_3$
$(D)$ $NaOCl$