During Class Invention

During class display all the results obtained by the students from the BCE and ask the students to describe any patterns they see in the data Based on the experiments we designed students should see;

1) that doubling the time double the mass of metal produced;

2) that increasing the amps by a factor of 1.5 increases the mass produced by a factor of 1.5; (expect most student will only recognize that increasing the amps increase the mass produced);

3) the third pattern is more complicated where the amps and times are held constant but the nature of the metal is changed; to see this relationship students must determine the change in amount must be expressed in moles. This can be established by expressing the reaction at the cathode as a reduction half-reaction. (review the microscopic videos to see that the change in amounts are in terms of atoms, not mass: the kinds of questions that could asked to evoke this idea include: ???) (once moles are established it might be useful to review the first two patterns (1 and 2) in terms of moles:) Once the change in amounts are expressed in moles the students will see a factor of two difference between the moles of Zn produced compared to the moles of Ag produced. Now students have to see it is the number of electrons transferred that the two is discovered.

Now that we know the amount of metal plated is inversely proportional to the number of electrons transferred we can explore the numbers:

moles of metal plated (is proportional to) (amps * time)/number of electrons transferred

However in the equation above the moles plated are not equal. to convert the proportionality to an equality we must introduce a constant, that constant when placed in the denominator is 96,500 and is called the Faraday.

Eventually the set of experiments invents the relationship that moles of metal produced = (amps * time)/(moles electrons transferred* Faraday's Constant)