The sulphate of a metal M contains 20% of M. This sulphate is isomorphous with ZnSO4.7H2O. The atomic weight of M is

Q: The sulphate of a metal M contains 20% of M. This sulphate is isomorphous with ZnSO4.7H2O. The atomic weight of M is

(A) 12

(B) 24

(C) 36

(D) 48

Sol: Equivalent of metal sulphate = Equivalent of metal

$\large \frac{Wt. \; of\; metal\;sulphate}{Eq.\; Wt. \; of\; metal\;sulphate} = \frac{Wt. \; of\; metal}{Eq.\; Wt. \; of\; metal} $

$\large \frac{W_{metal \; sulphate}}{E_M + E_{sulphate}} = \frac{W_M}{E_M} $

$\large \frac{W_{metal \; sulphate}}{W_M} = \frac{E_M + 48}{E_M} $

$\large \frac{100}{20} = \frac{E_M + 48}{E_M} $

EM = 12