A certain hydrate has the formula ${MgSO}_4·{xH}_{2}O$. A quantity of $\mathbf{54}\mathbf{.}\mathbf{2}\mathbf{ }\mathbf{g}$ of the compound is heated in an oven to drive off the water. If the steam generated exerts a pressure of $24.8 atm$ in a $2.0 L$ container at $120°C$, calculate $x$

 Applying idea gas equation

$pv=nRT$

weight $=54.2$

Molecular weight $=120+18x$

Pressure $=24.8$

Volume $=2 L$

Temperature $=393k$

$24.8\times 2=\frac{\text{ given mass }}{\text{ molar mass }}\times 0.0821\times 393.$

$24.8\times 2=\frac{x\times 54.2}{(120+18x)}\times 0.0821\times 393.$

After solving this equation, we get the value of x= 6.95.

Therefore, option D is correct.