The amount of  Mg in gms to be dissolved in dilute H2SO4 to liberate H2 which is just sufficient to reduce 16.0 gm of Ferric oxide into iron is

I. Fe2O3+3H2→2Fe+3H2O II. Mg+H2SO4→MgSO4+H2 I. 160gm  Fe2O3→3mole  H2 16.0gm  Fe2O3→? =0.3mole H2 II. 1mole H2 obtained from →24gm​​  Mg 0.3mole H2 obtained from →? =241×0.3=7.2gm  Mg