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Electrochemistry
Solving a problem you’ve never seen before and for
which you have no formula.
Produced by Mr. DoddridgeMurrieta Valley High School
What’s the most important thing in chemistry?
Units
Keeping Mr. D happy!
Units
Keeping Mr. D. happy!
This is a good thought. Although it is very important, it’s probably only #2.
Try again
Right!
So let’s proceed to a problem keeping this in mind and not panicking
Proceed (next)
Question:
How much copper can be plated in 30 minutes at 10 amps? (Cu+2 + 2e- → Cu)
What are we being asked? What unit? Were you thinking:
grams?
Next
What are some facts you know?
Next
1 amp = 1Coulomb/second 1Faraday = 96485 Coulombs/mole e-
Mass of copper = x g/mole (What’s x ?) (Where would you find it?) Were you thinking:
the periodic table?
Do you remember the question?
How much copper can be plated in 30 minutes at 10 amps? (Cu+2 + 2e- → Cu)
The facts:
10 amps in 30 minutes
1 amp = 1 C/s
1 F = 96,485 C/mole e-
1mole e- = how many moles Cu? (Cu+2 + 2e- → Cu)
1 mole Cu = X grams Cu?
Next
What’s the given?
=
30 minutes 10 ampsor
given
What’s the given?
10amps = 10 coulombs/ secondThis might work, but let’s try dealing with the time first.
=
30 minutes 10 amps
Good! Now what goes here?
30 min=
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
Try Again.Remember: units must cancel
30 min=
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
Good! Now what goes here?
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec=
What will cancel “seconds”?
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec=
Good! Now what goes here?
1 sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10Coulomb=
Hint: I shortened Coulomb to C
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10Coulomb=
Good! Now what goes here?
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10Coulomb=
1 Coulomb
1 mole e-
Come on now! We’re almost finished.
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10Coulomb=
1 Coulomb
1 mole e-
Stop kidding around!
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10Coulomb=
1 Coulomb
1 mole e-
Finally! Now what could possibly
go here?
sec10 Coulomb/
1 min60 sec/ 96,485 C/1 mole e-1F=
/2 mole e-1 mole Cu(s)
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
=
Care to try again?
1 mole Cu(s)63.5 g Cu/
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
=
Alright! So, what’s the answer?
23.7 g Cu
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
1 mole Cu(s)
63.5 g Cu=
5.92 g Cu or
Calculator error.Try again.
23.7 g Cu
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
1 mole Cu(s)
63.5 g Cu=
5.92 g Cu
Right! Remember the question?
How much copper can be plated in 30 minutes at 10 amps?
We were expecting an answer in grams.
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
1 mole Cu(s)
63.5 g Cu= 5.92 g Cu
Right! Remember the question?
How much copper can be plated in 30 minutes at 10 amps?
We were expecting an answer in grams. Click here to see how things cancel.
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
1 mole Cu(s)
63.5 g Cu= 5.92 g Cu
Right! Remember the question?
How much copper can be plated in 30 minutes at 10 amps?
We were expecting an answer in grams. And that’s the only unit that didn’t cancel.
30 min
1 min
60 sec
1 sec
10 Coulomb
96,485 C
1 mole e-
2 mole e-
1 mole Cu(s)
1 mole Cu(s)
63.5 g Cu= 5.92 g Cu
Want to try some more?
Click below to go to a site where you can get more practice
More Practice
