Question

How many moles of electrons are required to reduce one mole of nitrogen gas (N2) to two moles of nitrogen ions (N3-)?

Answer 1

Start by writing the atoms balance:

$N_{2} -\ \textgreater \ 2N^{3-}$

Now, determine the change of oxidation states:$N_{2}$ has oxidation state 0, so each N has to gain 3 electrons to become $N^{3-}$.

That, means that you need 6 electrons to balance the charges, resulting in:

$N_{2} + 6 e^{-} -\ \textgreater \ 2 N_{3-}$

And the answer is 6 mole of electrons.