The electrical charge of an electron, Q e , can be determined through a simple p
ID: 936910 • Letter: T
Question
The electrical charge of an electron, Qe, can be determined through a simple plating operation using an electrolytic cell. The technique is straightforward and requires that we plate a mass of copper onto an electrode from a copper sulfate solution. Since in solution, the copper ion, Cu++, has a positive 2 charge, it is required that 2 electrons react with the ion for every copper atom plated on. From elementary electricity (see section 20.11), the amount of coulombs that have passed along a wire or through a solution is given by:
Qtotal = current * seconds
or, Q total = I * time
where Q total = N * Qe
and N is the total number of electrons that have traveled in the circuit.
We will determine the number of electrons that have traveled through our electrolytic cell, N, by using the amount of copper plated on and Avogadro?s Number. From a value for N and knowing the current (i) and the time of plating we cn determine the charge of the electron Qe
This technique requires the use of Avrogadro?s Number ? a quantity not fully know with great precision until after Milliken performed his famous Oil Drop Experiment.
Pre-trial weight of Copper
13.987 grams
Post-trial weight of Copper
14.183 grams
Current
0.054 amperes
Initial Time
05:21 pm
Final Time
08:24 pm
Elapsed Time
10980 seconds
To calculate the total coulombs that have flowed, we use the above formula:
Q total= I x T
Q total= 3 amperes x 10980 seconds = 32,940 Coulombs
Next, we'll need to calculate the number of electrons during this electrolysis:
(32940 coul) x (1 electron / 1.6022 x 10^19 coul) = 2.056 x 10^23 electrons
Using the previous step, we can now calculate the number of Copper atoms plated on.
(2.056 x 10^23 electrons) / (2) = 1.028 x 10^23 Copper atoms
Pre-trial weight of Copper
13.987 grams
Post-trial weight of Copper
14.183 grams
Current
0.054 amperes
Initial Time
05:21 pm
Final Time
08:24 pm
Elapsed Time
10980 seconds
Explanation / Answer
to calculate the charge of one electron you have to divide the total charge (in Coulumb) with the total number of electrons:
32940/2,056.10*23=1,602140078.10*-19
this is the charge of one electron
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