Redox Stoichiometry
lesson 7
chapter 13
Objective
You will be able to calculate masses, volume
and concentration from redox reactions.
Faraday's Law
The amount of substance produced or
consumed in an electrolysis reaction is directly
proportional to the amount of charge (number of
electrons) that flow through the circuit.
I = current (amperes or coulomb/second)
t= time (seconds) (1 hour = 3600 seconds)
F= Faraday's constant = 9.65 x 104 C/mol
(in Data Book)
Example 1
A current of 2.50 amps flows for 20.0 seconds, how
many moles of electrons flow during this time?
Example 2
Convert a current of 2.00 amps for 25.0 min into an
amount of electrons.
Example 3
In a half reaction, electrons can be a reactant or product,
and can be part of a mole ratio.
The Reduction of Copper (II) Ions
Example 4
What mass of cobalt can be produced if a solution of
cobalt (II) nitrate is electrolyzed with a current of 15.0
amps for 1.00 h?
Example 5
How many minutes will it take to plate 25.0 grams of
copper metal onto a cathode if the current is 10.0
amps?
Example 6
Predict the current required to produce 15.0 kg of
aluminum per hour in an aluminum refinery.
Example 7
What volumes of H2 and O2 are produced at SATP from
the electrolysis of water by a current of 2.50 amps in
15.0 minutes?
Example 8
In a silver-zinc voltaic cell the mass of each electrode
was initially 10.0 g. If the anode decreases in mass by
4.50 grams, what is the final mass of the cathode?
If a current of 500 mA was created, how long did this
process last?
Assignment
Read text p. 514-516
Do practice problems 9-12