8.6g of an oxide of a metal reacts completely with hydrogen gas to yield 1.8g of water. The equivalent weight of metal is

MgO + H2 → Mg + H2O

Let the oxide of metal be MgO (M. wt = 40.3044) 
metal is Mg ((M. wt = 24.305)

Eq wt of metal = 24.305/2
                          = 12.15
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