c
અહીં, \(ZnSO_4 \times 7H_2O\)  અને  \(MSO_4 \times  7H_2O\) સમસ્ફટીકીય હોવાથી 

\(MSO_4×7H_2O\) \(= m + 32 + 64 + 126 = m + 222\)

તથા \(\,\% \,M = \frac{m}{{m +222}} \times 100 = 9.87\,\) (જે આપેલ છે.)

\(\therefore \,\,\,100\,m = 9.87\,m\, + \,222\, \times \,9.87\,\)

\(\,\therefore \,\,\,\,90.13\,m = 222\, \times \,9.87\,\,\,\)

\(\therefore \,\,m = \frac{{222 \times \,9.87}}{{90.131}} = 24.3\)