07:Posttest 07.Cherical Reactions
3. For a reaction to occur, energy must be
to break chemical bonds.
O released
absorbed
ons
converted

Al (s) + 3Fe3+ (aq) ---> Al3+ (aq) + 3Fe2+(aq)

Explanation:

atoms become positive (or less negative) ions when they lose electrons. They become negative (or less positive) ions when they gain electrons, since each electron (e-) has a charge of -1.

So, since Al changes to Al3+ which is positive, it loses electrons. And when Fe3+ changes to Fe2+, it becomes less positive, so it gained electrons.

Now, write the half (balanced) equations:

Al ---> Al3+ + 3e-

Fe3+ + e- > Fe2+

To combine both equations, we have to eliminate electrons. To do so, make sure both half equations have the same no. of electrons. We can multiply the equation of Fe by 3 so that it has 3 electrons.

3Fe3+ + 3e- > 3Fe2+

Finally, we can combine both equations (remember to eliminate the electrons).

Al (s) + 3Fe3+ (aq) ---> Al3+ (aq) + 3Fe2+(aq)

Check to see if both sides of the equation have equal charges. Ions always have an aqueous state.