A certain metal whose equivalent mass is 28 gm displaces 0.7 lit of H₂ at S.T.P. from an acid, the mass of metal is

1 equivalent of metal must liberate 1 equivalent of H₂

28 gm of metal liberates -----------  11.2 lits of H₂ at STP ( volume equivalent of H₂ at STP = 11.2 lit)

  ?    ---------------------------------------0.7 lit of H₂ at STP

= $\frac{28\times 0.7}{11.2}=$1.75 gm