A first row transition metal \( (M) \) does not liberate \( \mathrm{H_2} \) gas from dilute \( \mathrm{HCl} \). \( 1 \) mol of aqueous solution of \( \mathrm{MSO_4} \) is treated with excess of aqueous \( \mathrm{KCN} \) and then \( \mathrm{H_2S(g)} \) is passed through the solution. The amount of \( \mathrm{MS} \) (metal sulphide) formed from the above reaction is \( \_\_\_\_\_\_ \) mol.
