Inside a chemical battery it is not actually individual electrons that are transported from the + end to the − end. At the + end
of the battery an “acceptor” molecule picks up an electron entering the battery, and at the − end a different “donor”
molecule gives up an electron, which leaves the battery. Ions rather than electrons move between the two ends to transport
the charge inside the battery.
When the supplies of acceptor and donor molecules are used up in a chemical battery, the battery is dead, because it can no
longer accept or release electrons. The electron current in electrons per second, times the number of seconds of battery life,
is equal to the number of donor (or acceptor) molecules in the battery.
A flashlight battery contains approximately half a mole of donor molecules. The electron current through a thick filament
bulb powered by two flashlight batteries in series is about 0.3 ampere. About how many hours will the batteries keep this
bulb lit?