Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Connor Wilson
Katarina Ong
Michael Oliver
8 April 2014
Investigation 43 : What are the Metals?
Experimental Background
A company that specializes in battery production wants analysis of four unknown metals
...
the predicted identification of each metal (and its
accompanying salt solution), and 2
...


Materials

Equipment

Four Unknown Metals

Spot Plate

Associated Salt Solution of Unknown Metals

Test Leads (for digital voltmeter)

Salt Bridge Solution (1
...
​ This image shows the four unknown metals, as well as the test leads that were
hooked up to the voltmeter
...
​ This image shows the spot plate containing the metal salt solutions corresponding to
each metal shown in figure 1
...
​ This image is a simple diagram showing how each cell was constructed, with two
metals connected to the voltmeter and resting in their corresponding salt solution, connected by
a salt bridge
...
The collection of the qualitative
appearance of the metals is found ​Table 1​
...
This assumption then served as a reference point in the
calculations, but was also verifiable
...

Table 1​
...

Metal

Color

Luster

M1

orange/brown moderate
(copper)
luster

M2

silver/white
(light grey)

dull

M3

dark grey

dull

M4

silver
(light gray)

shiny

Density
(relative)

Hardness

Solution

soft (thin foil)

bright blue
colorless

heavy

soft/ductile

colorless
dark grey/
black

In order to identify each metal, a combination of two metals (with their associated salts) needed
to be tested
...
The test was
performed by soaking a string (twine or yarn) in sodium nitrate, then bridged between two
solutions
...
The resulting galvanic cell created a voltage
as shown in ​Figure 3​
...
When the tests were performed, DataLogger was set to record
the voltage 3 times per second for 10 seconds
...
time was
to determine the average voltage as there was a (relatively small) swing in voltage
...
Each test was conducted in this manner, making sure that only the
metal and its associated salt were ever introduced
...


4

Data Collection
Table 2
...

M1

M2

M3

M4

M1

x

1
...
485V
Reduced: Metal
1
Oxidized: Metal
3

0
...
004 V
Reduced: Metal
1
Oxidized: Metal
2

x

0
...
372 V
Reduced: Metal
4
Oxidized: Metal
2

M3

0
...
469 V
Reduced: Metal
3
Oxidized: Metal
2

x

0
...
428 V
Reduced: Metal
4
Oxidized: Metal
1

1
...
905 V
Reduced: Metal
3
Oxidized: Metal
4

x

5

Data Processing
Because Metal 1 was identified as Copper from appearance alone, its reduction potential was
used for the equation:
E 0 cell = E 0 red + E 0 ox
...

Table 3:​ Summary of Calculated and Theoretical reduction potentials for the unknown metals
Metal

Calculated Reduction
potential ( E 0 red )
(measured in volts)

Theoretical
Reduction Potential
(from table)
(measured in volts)

Metal

1

N/A

0
...
664

-0
...
145

-0
...
768

0
...
Therefore,
its reduction potential would take the place of E 0 red
...

1
...
34V + E 0 ox
...
M 2 = 0
...
664V
Although this reduction potential is closer to Chromium ( which has reduction potentials of -0
...
73 V), it was decided that Metal 2 was Zinc because the qualitative observations better
matched Zinc than Chromium
...

While the reduction potential from Metal 1 was used to determine the reduction potentials of all
the other metals in their galvanic cells, the galvanic cells that did not include metal 1 (such as
the galvanic cell between 2 and 3) were used as a check
...
(M 3) + E 0 ox
...
were the calculated reduction potentials from Table 3
...
469V = (− 0
...
664V
0
...
519V
6

Conclusion and Evaluation
The purpose of this laboratory investigation was to determine the identities of four unknown
metals
...
With this quantitative data, along with educated
guesses related to the qualitative appearance of the metals, it was possible to identify the
metals, though with varying degrees of certainty
...
If we
assume that the unknown metals are indeed pure metals, as opposed to some alloy, the
distinctive color of copper allows it to be readily identified
...
In addition to these indicators, the salt
solution for metal one was bright blue, another indication that unknown metal one was indeed
copper
...
Metal two had a calculated reduction potential of - 0
...

This value was near the theoretical reduction potential for both zinc and chromium, but the
qualitative observations made about metal two more closely matched the properties of zinc
...
Because of this, metal two was identified as zinc
...
Metal three was dark
grey in color, dull, heavy(dense), and ductile, qualities which, when combined, strongly indicate
lead
...
145V, very near to the theoretical reduction potential of -0
...
Metal four, like metal
two, was a fairly indistinct silver-colored metal
...
This initial impression was further
strengthened, as the calculated reduction potential of 0
...
80V for silver
...

One significant limitation of this lab is the ever-present effect of resistance
...

Using materials with low resistance, or even superconducting materials, would yield more
accurate experimentally determined reduction potentials
...
Because of their small size (a spot plate was used to
contain the salt solutions and metals) it was difficult to adequately control the system, meaning
that the metals may have come into contact with the salt bridge or the edge of the spot plate, or
the test leads may have come into contact with the salt solution
...
scaling the
system up to the size of beakers would be more time-consuming, but would certainly allow the
system to be more easily controlled
...
This is shown in the
experimental data, as the combination of metal 2 (zinc) and metal 4 (silver) yielded the highest
cell potential
...


8



---