Plaster of Paris is used:

Which of the following does not react with cold or hot water?

$Mg(NO_3)_2 \cdot XH_2O$ and $Ba(NO_3)_2 \cdot YH_2O$ represent the formulas of the crystalline forms of nitrate salts. The sum of $X$ and $Y$ is $.........$.

Which one of the following pairs does not impart colour to the flame?

Deep pink colour is given to flame by the salts of

The most stable carbonate is