When balancing oxidation–reduction equations that occur in acidic aqueous solution, which of the following best explains why H+ ions are often added to one or both sides of the equation?
a) They neutralize any basic species that may be present in the reactant mixture.
b) They provide a source of protons that allows hydrogen atoms to be balanced without altering the charge balance.
c) They balance the total number of electrons transferred between the half-reactions.
d) They act as spectator ions to keep the ionic strength of the solution constant.