In the removal of temporary hardness of a sample containing $Ca^{2+}$,what is the number of moles of $Ca(OH)_2$ used per mole of $Ca(HCO_3)_2$ removed?

Statements about heavy water are given below.
$A.$ Heavy water is used in exchange reactions for the study of reaction mechanisms.
$B.$ Heavy water is prepared by exhaustive electrolysis of water.
$C.$ Heavy water has higher boiling point than ordinary water.
$D.$ Viscosity of $H_2O$ is greater than $D_2O$.

Which physical constant for $H_2O$ has a higher magnitude than $D_2O$?

Observe the following statements:
$1.$ Heavy water is harmful for the growth of animals.
$2.$ Heavy water reacts with $Al_4C_3$ and forms $\text{deuterated acetylene}$.
$3.$ $BaCl_2 \cdot 2D_2O$ is an example of $\text{interstitial deuterate}$.
The correct statements are:

Explain the structure of ice.

We use polymetaphosphates as water softeners as they: