Calcium hydride on hydrolysis forms?

What is meant by 'demineralised' water and how can it be obtained?

$A$ 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).

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T$.: $Na\underline{H} + H_2O \longrightarrow NaOH + H_2 \uparrow$

Identify the correct statements from the following.
$A$. In photosynthesis reaction,water is oxidized to oxygen.
$B$. An example for interstitial hydride is $MgH_2$.
$C$. Sodium hexametaphosphate is used in the removal of permanent hardness of water.

Boiling of hard water is helpful in removing the temporary hardness by converting calcium hydrogen carbonate and magnesium hydrogen carbonate to ....