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RYAN INTERNATIONAL SCHOOL,
GHAZIABAD
INVESTIGATORY
PROJECT ON:Calculating Gibbs Free energy for redox
reactions
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INDEX
S no.
TOPICS
1. ACKNOWLEDGEMENT
2. CERTIFICATE
3. INVESTIGATORY PROJECT REPORT
(i)
Aim
(ii) Introduction
(iii) Materials required
(iv) Theory
(v) Procedure
(vi) Observations and Calculations
(vii) Conclusion
(viii) References
Page no.
3
4
6
6
7
7
8-9
10
11
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ACKNOWLEDGEMENT
On completion of my investigatory project I feel
extremely delighted but it wasn’t a single effort.
First of all I would like to thank my parents for
helping me and encouraging me to continue this
project and helping me financially as well. Then I
would like to thank my teacher Mr. Ranjeet Singh
Vyas for teaching me the basics of this investigation.
I would also like to thank my chemistry teacher Ms.
Preeti Jain for supporting me and giving me the
opportunity to make this project. In the end I would
like to thank the vegetable vendor, cyber café
owner, and Drishti stationeries for providing me
with fresh potatoes, printouts and spiral binding
respectively.
Shivam Shekhar
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CERTIFICATE
This is hereby to certify that the original and
genuine investigation work has been carried
out to investigate about the subject matter and
the related data collection and investigation
has been completed solely, sincerely and
satisfactorily by SHIVAM SHEKHAR of CLASS XII
– A, Ryan International School, GHAZIABAD,
regarding his project titled “Calculating
Gibbs Free energy for redox reactions”.
Teacher’s Signature
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INVESTIGATORY
PROJECT
ON:Calculating Gibbs Free energy
for redox reactions
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1. Aim:To calculate Gibb’s free energy for a redox reaction with the help of
electrochemical cell using various electrodes by calculating the value of
its EMF.
2. Introduction:Many chemical reactions we observe around us are basically redox
reactions only, occurring in one or the other way. To understand the
concepts of redox reactions I am using the electrochemical cell method
because it gives a very clear picture of what redox reactions are all
about (plus it’s cheap too!!!).
Now something about my experiment, I am going to make an
electrochemical cell using a potato as electrolyte and metals like iron,
Aluminum and copper as electrodes and calculating the value of free
energy for a redox reaction by using equation:∆𝐺 = −𝑛𝐹𝐸𝑐𝑒𝑙𝑙
Where; E = EMF of the cell
n = no of electrons transferred from anode to cathode in the
Reaction equation
F= Faraday constant
𝜟G=free energy for redox reaction
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3. Materials Required:(i)
(ii)
(iii)
(iv)
(v)
(vi)
1 potato
An aluminum sheet wrapped on a toothpick
An iron nail
A copper coin
A multimeter
Space to work
4. Theory:Potatoes contain several compounds like chlorogenic acid,
caffeoylquinic acid, etc. which act as an electrolyte in the experiment.
Copper coin, iron nail and aluminum sheet act as electrodes.
According to the electrochemical series, amongst iron, copper and
aluminum the value of reduction potential are: Reaction
Eo(Reduction potential)
Al3++3e-→Al(s)
-1.66 V
2+
Fe +2e →Fe(s)
-0.44 V
2+
Cu +2e →Cu(s)
0.34 V
It is clear from the above table that 3 metal couples could be formed
i.e. Copper-Aluminum, Copper-Iron, Aluminum-Iron
Now using equation,
∆𝐺 = −𝑛𝐹𝐸𝑐𝑒𝑙𝑙
We can find the value of E with the help of multimeter, F is already known, n
we can get from reaction equation and using all those values we can calculate
the value of 𝜟G.
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5. Procedure:(i)
(ii)
Take the potato and insert the iron nail into it and take a copper
coin and insert it into the potato.
Now take the multimeter and adjust it to measure voltage of the
order of 0 to 2000 mV. The following picture depicts the
procedure.
Copper coin
Iron nail
Knob at 2000mV position
(iii)
(iv)
Fix the multimeter terminals into the potato such that they touch
the electrodes and note the reading.
Repeat the same experiment with Al-Fe and Al-Cu couples and
note their readings as well.
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With Cu-Al couple:-
Toothpick wrapped with
aluminum sheet
Copper coin
With Al-Fe couple:-
Toothpick wrapped with
aluminum sheet
Iron nail
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6. Observations and calculations:From above experiment, we get the following readings:Metal couple
EMF(in mille volts)
Cu-Al
457
Cu-Fe
563
Al-Fe
398
Now for Cu-Al couple,
The reaction is:2Al→2Al3++6e3Cu2++6e-→3Cu
2Al+3Cu2+→3Cu+2Al3+
Hence 6e- are transferred in the reaction.
Now using the formula we have
∆𝐺 = −𝑛𝐹𝐸𝑐𝑒𝑙𝑙
∆𝐺 = −6 ∗ 96500 ∗ 0.457
∆𝐺 = −264603 𝐽𝑜𝑢𝑙𝑒𝑠
𝜟G=-264.603 KJ
Similarly for other couples,
Couple Reaction
Cu-Al
3Cu2++2Al→3Cu+2Al3+
Cu-Fe
Cu2++Fe→Cu+Fe2+
Al-Fe
2Al+3Fe2+→2Al3++3Fe
EMF
0.457V
0.563V
0.398V
𝜟G=-nFEcell
-264.6KJ
-108.7KJ
-230.4KJ
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7. Conclusion:From above experiment it is concluded that free energy change for
various metal couples are:𝜟G
-264.6KJ
-108.7KJ
-230.4KJ
Couple
Cu-Al
Cu-Fe
Al-Fe
8. References:




En.wikipedia.org
Google.co.in
Chemistry part 2nd class 11th NCERT
Chemistry part 1st class 12th NCERT
All the pictures have been clicked by Nokia 2700 classic 2 MP
camera with resolution of 1200x1600
 All tables along with this project have been created with the help
of Microsoft Word 2007