What mass of Cu(s) would be produced if 0.40 mol of CuX2O(s) was reduced completely with excess HX2(g) ?
Approach
We first need to write the balanced equation. The oxidation state of copper changes from +1 to 0.
CuX2O(s)reductionCu(s)
The other reactant must be oxidized. The oxidation state of hydrogen will increase. Water will be the likely product since we need a compound with hydrogen and oxygen.