Given the balanced equation representing a reaction: #Mg(s) + Ni^(2+)(aq) -> Mg^(2+)(aq) + Ni(s)# What is the total number of moles of electrons lost by Mg(s) when 2.0 moles of electrons are gained by #Ni^(2+)#(aq)?

1 Answer


There are also 2.0 moles of electrons lost from Mg.


Since the equation is balanced, the reactants (and their total charge) must equal the products and their overall charge.

In other words, nothing is lost during the reaction.

In this reaction, magnesium is oxidized and nickel is reduced.

The electrons are transferred from magnesium to nickel and because electrons have a negative charge, this results in #"Ni"^"2+"# becoming neutral #"Ni"#.

Because the magnesium lost the two electrons, it now becomes #"Mg"^"2+"# because there are now 2 more protons than electrons,

(in a neutral atom the number of electrons = the number of protons)

Thus resulting in the 2+ charge.