The percentage of H2 in the hydride of an element  having equivalent weight 11.5 is:

Eq. wt. of element = 11.5;  let wt. of metal =x g;wt. of element =  100 - x g; Eq. wt. of H2=1.008.We know that:      Wt. of element  Wt. of hydrogen = Eq. wt. of metal  Eq. wt. of H2(=1.008)or   100−xx=11.51.00811.5x=100.8−1.008x ; 12.508x=100.8∴         x=100.8/12.508=8.06∴ Percentage of H2=8.06%