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

What is not true about ice?

How many hydrogen atoms are surrounding each oxygen atom in the structure of ice?

Which of the following reactions is not an example of a hydrolysis reaction?

Some statements about heavy water are given below:
$(i)$ Heavy water is used as a moderator in nuclear reactors.
$(ii)$ Heavy water is more associated than ordinary water.
$(iii)$ Heavy water is more effective solvent than ordinary water.
Which of the above statements are correct?

Which salt does not produce hardness in water?