An inorganic compound first melts,then resolidifies,and then liberates a gas. It may be

The density of a liquid is $1.5 \, g/mL$. There are $50 \, drops$ in $5 \, mL$. The number of molecules in $1 \, drop$ is (molecular weight of liquid is $100$).

Partially dried soil contains $50 \%$ silica and $7 \%$ water. If the original soil contained $12 \%$ water,then the percentage of silica in the original soil is .............. $\%$.

The ratio of the number of water molecules in Mohr's salt and potash alum is $.... \times 10^{-1}$.

Ferric alum has the composition $(NH_4)_2SO_4 \cdot Fe_2(SO_4)_3 \cdot xH_2O$,where $x$ is..........

The number of electrons in one molecule of urea $(NH_2CONH_2)$ is