Chemistry Project

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Chemistry Project
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Schools Name
Chinese YMCA Secondary School
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Teacher's Name
Ho Wing Leung
Group Name
Mercury Penny 5 (MP5)
Group Leader
SZE HIU SHING
Group Members
LIU CHI WAI POON CHI HO CHAN SHING HEI TSE HIU
CHUNG
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Title
The Myth of Mercurochrome
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Main Objective
Investigate the method of finding the amount of
Mercury in Mercurochrome
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Introduction
The structure of and information about
Mercurochrome
Colour Red Empirical formula C20H8Br2HgNa2O6 For
mula weight 750.66
The use of Mercurochrome
The Hg2 in mercurochrome can make protein
solidify and precipitated.Therefore having an
effect of antibacterial. But nowadays it is
rejected to use it because it is toxic.
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The principle of the experiment
We put coins into the Mercurochrome solution and
then heat them. We finally find that mercury
deposits on the surface of coins. The mechanism
in this experiment involved is a redox reaction.
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Reducing agent copper and nickel on the
coins. Oxidizing agent Mercurochrome. In the
solution, the following reactions take place Cu
Hg2 ? Cu2 Hg Ni
Hg2 ? Ni2 Hg When
Mercurochrome comes into contact with the coins,
metallic Hg will be spontaneously depositied on
the coin with the release of Cu2(aq) and
Ni2(aq) Mercury then form alloy with Copper and
Nickel.
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Apparatus and chemicals
Coins (10c) Dilute HCl Beakers Aluminum
foil Mercurochrome Baking soda (NaHCO3)
Brand of sample used in the market
Kamsing Medicine Company
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The First Laboratory Section
Objective Finding out if aluminum foil container
was necessary
Procedure 1. Clean 1 coin with detergent and
soak in a dilute solution of HCl in a small
beaker for removing rust, dirt. Weight the coin
by electronic balance 2. Put the coin in the
center of the container in different ways. (
The methods will be told in the Results part) 3.
Add in 40cm3 Mercurochrome and 60cm3water. 4. 2g
of NaHCO3 into the container. 5. Heat the mixture
with small flame. Turn off the burner. 6. Pick
out the coin and allow it to dry, then weight it
by electric balance. Finally find out the weight
difference.
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Results Observation
During boiling the solution with the coin, the
red colour became lighter. And silvery mercury is
found on the surface of coin.
Data 1 (Put the coin in the glass beaker with no
aluminum foil) Mass of mercury deposited 0g
Data 2 (Put the coin in the glass beaker with a
piece of aluminum foil touching it) Mass of
mercury deposited 0g
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Data 3 (Put the coin in the glass beaker with
the aluminum foil at the bottom of the
glass) Mass of mercury 0.02g
Data 4 ( Put the coin in the beaker with a piece
of aluminum foil covering the coin) Mass of
mercury 0.01g
Data 5 (Put the coin in the aluminum
container) Mass of mercury 0.02g
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Discussion
We found that without the aluminum foil as the
container, the amount of the mercury deposited on
the coin would be very small or even none.
Actually, the necessary of aluminum is still
unknown.
Difficulties

• There is leakage of aluminum container. The
  container is not strong enough to resist the
  weight of solution.
• So we use stronger aluminum containers for
  further experiments.

2. There is insufficiency of surface area of
coin. We modified the procedure that to increase
the number of coins for the experiment.
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The Second Laboratory Section
Objective Finding if the amount of mercury
deposit on the coins was proportional to the
concentration of Mercurochrome used.

• Procedure
• It is same as that of Day 1, besides
• Use 3 coins for each experiment
• Concentration of Mercurochrome is different.
  (Refer to the table in Result part)

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Results Observation
The amount of mercury deposited on the coins,
were different with different concentration of
Mercurochrome.
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Discussion
It was found that the concentration of
Mercurochrome used would affect the amount of
mercury deposited. For more concentrated
Mercurochrome , the more mercury is found.
Difficulties
1. The insufficient accuracy of the balance used
The electric balance in school only can show up
to 2 d.p. So we went to City University to use a
4 d.p. electric balance for accurate results.
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2. The concentration of Mercurochrome used was
not enough. So we decided to have 50cm3 of
Mercurochrome and 50cm3 of water to do each
experiment.
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The Third Laboratory Section
Objective Find out the relationship between the
time taken of the experiment and the amount of
mercury deposited.

• Procedure
• It is same as that of Day 12, besides
• Use 5 coins for each experiment
• Concentration of Mercurochrome is changed. (
  50cm3 of Mercurochrome and 50cm3 of water)

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Results Observation
We did twice during 3rd day experiment
Data 1 (spent 10 minutes in heating
process) Mass of mercury deposited
0.0089g Data 2 (spent 5 minutes in heating
process) Mass of mercury deposited 0.0007g
Comparing the above data, more mercury is coated
on the surface of coins in data 1 than that of in
data 2
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Discussion
The relationship between the time taken of the
experiment and the amount of mercury deposited
The longer time in heating, the more mercury can
deposit.
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Main Result
The result below is about comparing of amount of
mercury found experimentally and from information
provided by company.
Result found experimentally Mass of mercury
found 0.0089g No. of moles of mercury 4.44 ?
10-5moles Information from company No. of moles
of Hg atoms in sample( 50cc) 8.91 ?10-4 moles
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Final discussion

• In main result, the amount of Hg atoms we found
  were not the same. It may due to
• The number of coins used was still not enough.
• The time taken in the heating process was not
  long enough.

The use of NaHCO3 To maintain the pH of the
reaction to slightly basic.
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Acknowledgement
University Grants Committee
In City University of Hong Kong Department of
Biology and Chemistry City University of Hong
Kong General Office and Laboratory Education
Office (Dr. Joe Hong) Faculty Laboratory Centre
(POP bulletin board) Student Development
Services Prof. David Randall (Principal Project
Coordinator) Dr. Paul Shin (Deputy Project
Coordinator) Project Supervisors (Prof. Nora Tam
and Dr. Paul Shin for wetland group / Dr. Michael
Lam for chemistry groups) Project Coordinator
Sylvia Lee Student mentor Vincent Lo