Temperature of maximum density of $H_2O$ is $y \ K$ and $D_2O$ is $x \ K$. $(x-y)$ (in $K$) is nearly

We use polymetaphosphates as water softeners as they:

$D_2O$ is used more in

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

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

When chlorine water is exposed to sunlight,$O_2$ is liberated. Hence