Permanent hardness of water can be removed by

Which of the following substances is used in the laboratory to dry natural gas quickly?

The temporary hardness of a water sample is due to compound $X$. Boiling this sample converts $X$ to compound $Y$. $X$ and $Y$,respectively,are

Identify the statements which are not correct from the following:
a) In the structure of ice,each oxygen atom is surrounded by $4$ other hydrogen atoms via hydrogen bonding.
b) Temporary hardness of water is due to dissolved $Mg(HCO_3)_2$ and $Ca(HCO_3)_2$,not $NaHCO_3$.
c) In the reaction of acidified $KMnO_4$ and $H_2O_2$,$H_2O_2$ acts as a reducing agent.
d) $3 \ g \ L^{-1}$ $H_2O_2$ is not equal to $100$ volume $H_2O_2$ (since $100$ volume $H_2O_2$ is approximately $303.7 \ g \ L^{-1}$).

Molecular weight of heavy water is

$A$ sample of water contains $30 \ ppm$ of $MgSO_4$ and $19 \ ppm$ of $MgCl_2$. Calculate the hardness of water in $ppm$ (in terms of $CaCO_3$ equivalents).