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Determining Avogadro's Number Lab

Extracts from this document...

Introduction

Arianna S. Abundo

Chemistry IBS1-D

Mrs. Zimmerman

November 12, 2007

Determining Avogadro’s Number Lab

Data Collection

Table 1.  Table showing initial mass, final mass and qualitative observation of copper electrodes.

Electrode 1

Electrode 2

Initial Mass (g)

±0.005 g

5.77

5.80

Final Mass (g)

±0.005 g

6.27

5.27

Observations

The copper electrode is shiny after being placed in copper sulfate.  It also appears to have become thicker.

The copper electrode is dull after being placed in copper sulfate.  It also appears to have become thinner and rusty.

Table 2.  Table showing current of copper electrodes in 600 second intervals.

Time (seconds)

±5 seconds

Current (amps - A)

±0.05 A

0

1.1

600

0.7

1200

0.9

1800

1.0

Note:  As both copper electrodes were placed in a single beaker of copper sulfate, the data obtained for the current is the same for both electrodes.  Thus, the “Current” column in Table 2 represents the current of both copper electrodes.

Table 3.  Table showing voltage used during the experiment.

Voltage (volts)

±0.5 V

6

Data Processing

image00.png

Moles:

Number of moles

image01.png

image08.png

image15.png

image02.pngElectrode 2, which lost 0.53 grams after being placed in copper sulfate, contains approximately 0.00834 moles of copper.

Uncertainty of moles

Uncertainty of mass  =  Uncertainty of initial mass + Uncertainty of final mass

Uncertainty of mass  =  0.005 g + 0.005 g

Uncertainty of mass  =  0.

...read more.

Middle

  ≈  11.1%

image02.pngThe percent uncertainty for the average current is approximately 11.1%.  Thus, the average current after 10 minutes is 0.9 A ±11.1%.

After 20 minutes

Average current  =image03.png

Average current  =  0.8 A

Percent uncertainty of average current  =  image04.png

Percent uncertainty of average current  ≈  12.5%

image02.pngThe percent uncertainty for the average current is approximately 12.5%.  Thus, the average current after 20 minutes is 0.8 A ±12.5%.

After 30 minutes

Average current  =image05.png

Average current  =  0.95 A

Percent uncertainty of average current  =  image06.png

Percent uncertainty of average current  ≈  10.5%

image02.pngThe percent uncertainty for the average current is approximately 12.5%.  Thus, the average current after 20 minutes is 0.95 A ±10.5%.

Time:

Time  = 60  seconds  x  10 minutes

Time = 600 seconds

Percent uncertainty of time  =  image07.png

Percent uncertainty of time  ≈  0.833%

image02.pngThe percent uncertainty for time is approximately 0.833%.  Thus, the time after 10 minutes is 600 seconds ±0.833%.

Charge:

After 10 minutes

Average charge  =  average current  x  time

Average charge  =  0.9 A x 600 seconds

Average charge  =  540 C

Percent uncertainty of average charge  =  Percent uncertainty of current  +  Percent uncertainty of time

Percent uncertainty of average charge  =  11.1%  +  0.833%

Percent uncertainty of average charge  ≈  11.9%

image02.pngThe percent uncertainty for average charge is approximately 11.9%.  Thus, the average charge is approximately 540 C ±11.9%.

After 20 minutes

Average charge  =  average current  x  time

Average charge  =  0.8 A x 600 seconds

Average charge  =  480 C

Percent uncertainty of average charge  =  

...read more.

Conclusion

The electrode where the oxidation reaction takes place (loss of mass) is the anode, and the electrode that gained mass is the cathode.  The anode (Electron 2) gained copper electrons, and the cathode (Electron 1) lost copper electrons.  The copper electrons in the cathode move from the negative end to the positive end, and thus the reaction takes place.  

In our experiment, I noticed that the anode was rusty and thinner because it lost electrons.  This theory is proven by the weights we recorded in the experiment; the final mass of Electrode 2 was less than the initial mass.  

There were several errors in this experiment.  First, the electrodes were only given a few seconds to dry before we weighed them.  An error could have occurred by having an increase in mass because there was still acetone or water on the electrodes.  This can be improved by letting the electrodes dry fully before being weighed.

Another important error, which would have had major effects on the results, is human error.  If any of the calculations were incorrect, then the results would not match up with Avogadro’s number.

...read more.

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4 star(s)

This is a 4 star piece of work with excellent calculations and clearly laid out steps to calculate Avogadro's number. The layout of the investigation needs to be improved with suggestions for an aim, introduction, scientific information, prediction, method and risk assessment. If these improvements are done this would be a 5 star piece of work.

Marked by teacher Patricia McHugh 13/05/2013

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