The observed osmotic pressure for a 0.10 M solution of

The observed osmotic pressure for a $0.10 \mathrm{M}$ solution of $\mathrm{Fe}\left(\mathrm{NH}_{4}\right)_{2}\left(\mathrm{SO}_{4}\right)_{2}$ at $25^{\circ} \mathrm{C}$ is $10.8$ atm. The expected and experimental (observed) values of Van't Hoff factor (i) will be respectively $:\left(\mathrm{R}=0.082 \mathrm{~L}\right.$ atm $\left.\mathrm{k}^{-} \mathrm{mol}^{-1}\right)$