ap chemistry electrochemistry electroplating

1. The OPPOSITE OF BATTERIES?!
electroplating

2. Instead of MAKING electricity, we’re
using electricity to make a reaction run
“backwards” (Me means just some metal)
The - + in the red circle is the symbol
for a battery a source of electrical
energy. The battery forces electrons
into the system and into the metal.
The negative charge on the metal
attracts Cu+2 ions from the solution
to the metal and the Cu metal builds
up on the metal “coating” it in a thin
layer. This process is called
“ELECTROPLATING.”

3. Calculations! OUCH!
You have an OLD ALUMINUM KEY that you want to coat
with GOLD so that Donald Trump can use it. He only
likes golden keys. You are too cheap to buy a SOLID
GOLD KEY to give to him so you decide to
electroplate a thin layer of gold onto the aluminum….
How will you do this???
GOLD

4. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= seconds

5. Before calculations remember
• 1 amp = coulomb/second
• Or AS = C
• Gold Au+1 + 1e- → Au
• 96500 coulombs = 1 mole of electrons
• Gold has a molar mass of 197 grams/mole
• We only want to plate out 3 grams to save $$
• We have 20amps available
• FYI – normal home amperage is about 100amps

6. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= seconds

7. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= seconds

8. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= seconds

9. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= seconds

10. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= sec

11. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= sec

12. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= sec

13. THE BIG LINE 
First our data – you have a solution of Au+1 ions
with a gold electrode to use that contains only
3 grams of gold, a 20 amp source of electricity,
how long (IN SECONDS) should you let your
system run …??
= sec

14. Other ways to ask questions
I have some iron nails I want to electroplate with a layer of ZINC
(Zn+2 solution). Using my home amperage of 100 amps and
letting my system run for 30 minutes. How many grams of
zinc should plate onto my nails? (the process is called
“galvanizing” and it is used on nails so they don’t rust when
used outside!!)

15. homework
Ap chemistry book page 834
Problems 77, 79, 81, 83