A first row transition metal (M) does not liberate H_2 gas from dilute HCl. 1 mol of aqueous solution of MSO_4 is treated with excess of aqueous KCN…

A first row transition metal (M) does not liberate $\displaystyle \mathrm{H}_2$ gas from dilute HCl. $\displaystyle 1$ mol of aqueous solution of $\displaystyle \mathrm{MSO}_4$ is treated with excess of aqueous KCN and then $\displaystyle \mathrm{H}_2 \mathrm{~S}(\mathrm{~g})$ is passed through the solution. The amount of MS (metal sulphide) formed from the above reaction is $\displaystyle \_\_\_\_$ mol .