FARADAY’S LAW

• Using Faraday’s law, solve problems related to electrolytic cells

Additional KEY Terms

Faraday (1791-1867)

• Coined terms "electrode", "anode", "cathode", "electrolyte", "ion", "anion" and "cation"

Amount of product formed at each electrode is directly proportional to the amount of

current passed through the cell.

• I is the current in amperes (A)• Q is the charge transferred in coulombs (C)• t is the time in seconds (s)

Current (I)• 1 coulomb of charge moving per 1 second

I = Q t

You have to memorize this formula

1 coulomb is BILLIONS of electrons worth of charge

1 mole e- = 96 500 C

1 F = 96 500 C/mol e–

Faraday (F) – the charge of 1 mole of electronsA single e- has a charge of 1.60 x 10–19 C

This is also called Faraday’s constant

Summary: We can use the formula for current combined with Faraday’s constant to calculate the mass of products in an

electrolytic cell

Determine the moles of electrons supplied by a battery with a current of 0.100 A for 50.0 min.

Q = I · t

= 0.00311 mol e-300 C · 1 mol e–

96 500 C

0.100 · (50min x 60 sec/min)Q = 300 C

Calculate a mass of aluminum produced by 7.50 A passing through molten aluminum oxide for 6 hours, 20 minutes and 10 seconds.

Al3+ + 3e– → Al

Q = I · t

= 1.77 mol e-1.71 x 105 C· 1 mol e–

96 500 C

7.50 A · (22810 s)Q = 1.71 x 105 C

You will always need the formula for what your are producing – you need to know the ratio of electrons

needed

Once you have moles you can find mass – using molar mass

1 mol Al27.0 g Al 1.77 mol e-

3 mol e-

1 mol Al

= 15.9 g Al produced

Al3+ + 3e– → AlUse the ratio of electrons needed

Every other question type is a variation of this procedure (some might give the mass and ask you to work backwards to current or time – you will

always need the net ionic formula for the metal, the current formula, Faraday’s constant

CAN YOU / HAVE YOU?

• Using Faraday’s law, solve problems related to electrolytic cells

Additional KEY Terms