.
.
In the following
experiment the metals from the Cola cans are replaced by zinc (Zn) and
copper (Cu).
Weigh the electrodes at
the beginning and in the end of the experiment to measure what happens
with their masses during the flow of electricity.
What
you need: Scale, weights, Zn and of
Cu sheets, 2 insulated copper wires with 4 crocodile clips, digital
multimeter, 2 vials with copper and zinc salt solutions, wick from
tissue paper.
Experiment:
* Left: Weigh
the
metal sheets: Zn = 1.0 g, Cu 1.1 g.
* Photo 2: Dip
these
electrodes into the solutions of their
salts.
* Connect them to the
multimeter like in the previous experiment. * Dip the wick into the two
solutions.
Observations: The voltage reads 0.9 Volt. Photo 2:
The current
is 0.3 µA.
* Photo 3: Leave
the device for some days, while zinc and copper directly connected by a
wire.
Observations
Photo 3 and right:
The size (and mass) of the Cu electode has increased, the blue colour
fades, the mass of the Zn electrode decreased.
Explanations:
As an electron donor
zinc pushed electrons through the wire to the copper electrode.
Thes copper ions are
reduced: Zn(s) + Cu2+(aq) ----indirect redox reaction---> Zn2+(aq) + Cu(s)
Negative sulfate ions are
flowing to the zinc half cell via wick.