Solution NaH consists of Na⁺ and H^– ions. Since positive ions repel protons, the H^– ion is the only likely base. Again it may be useful to use two hypothetical steps: (l) donation of a proton by an H₂O molecule, and (2) acceptance of a proton by the base. As in Example 11.6, we can then sum the steps

`HOH -> cancelH + OH^(-)`      step 1

`H^(-) + cancelH^(+) -> H_2`             step 2
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`H^(-) + H_2O -> H_2 + OH^(-)`      overall

Note that adding a proton to H^– balances the excess electron of that ion, producing a neutral H₂ molecule. Note also that charges balance in all equations.