c
(c) As the given sulphate is isomorphous with \(ZnS{O_4}.7{H_2}O\) its formula would be \(MS{O_4}.7{H_2}O\,m\) is the atomic weight of \(M\), molecular weight of \(MS{O_4}.7{H_2}O\) \( = m + 32 + 64 + 126\) \( = m + 222\) Hence \(\%\) of \(M = \frac{m}{{m + 222}} \times 100\) \( = 9.87\)(given) or \(100\,m = 9.87\,m + 222 \times 9.87\) or \(90.13\,m = 222 \times 9.87\) or \(m = \frac{{222 \times 9.87}}{{90.13}} = 24.3\).