Question:
The ratio of number of water molecules in Mohr's salt and potash alum is $\times 10^{-1}$.
(Integer answer)
Solution:
Mohr's salt : $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Fe}\left(\mathrm{SO}_{4}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}$
The number of water molecules in Mohr's salt $=6$
Potash alum : $\mathrm{KAl}\left(\mathrm{SO}_{4}\right)_{2} \cdot 12 \mathrm{H}_{2} \mathrm{O}$
The number of water molecules in potash alum $=12$
So ratio of number of water molecules in Mohr's salt and potash alum $=\frac{6}{12}$
$=\frac{1}{2}$
$=0.5$
$=5 \times 10^{-1}$