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