The maximum number of hydrogen bonds formed by a water molecule in ice is

Assertion $(A)$ : $NaCl$ is less soluble in heavy water than in ordinary water.
Reason $(R)$ : Dielectric constant of ordinary water is more than that of heavy water.
The correct answer is

Permanent hardness due to $Mg^{2+}$ ions is best removed by

In the following reactions,the total number of oxygen atoms in $X$ and $Y$ is $........$.
$Na_2O + H_2O \rightarrow 2 X$
$Cl_2O_7 + H_2O \rightarrow 2 Y$

Which of the following is not correct for $D_2O$?

Melting point,enthalpy of vaporisation and viscosity data of $H_2O$ and $D_2O$ is given below.

$Property$	$H_2O$ vs $D_2O$
$Melting$ $point/K$	$273.0$ vs $276.8$
$Enthalpy$ $of$ $vaporisation$ $at$ $(373 \ K) / kJ \ mol^{-1}$	$40.66$ vs $41.61$
$Viscosity/centipoise$	$0.8903$ vs $1.107$

On the basis of this data,explain in which of these liquids intermolecular forces are stronger?