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Alchemy: copper into gold

Place your pre-1982 copper penny in an evaporating dish and heat with a mixture that first turns it silver, then suddenly turns it gold when the penny is then heated on a hot plate.

Caution: Wear safety goggles and gloves, do the reaction in the fume hood with the sash down. Note step 10: special disposal

  • Place approximately 5 g of zinc in an evaporating dish.
  • Add enough NaOH solution to cover the zinc and fill the dish about one-third.
  • Place the dish on a hot plate and heat until the solution is near boiling.
  • Prepare a copper penny (pre-1982) by cleaning it thoroughly with a light abrasive (steel wool pads work well).
  • Using crucible tongs or tweezers, place the cleaned penny in the mixture in the dish.
  • Leave the penny in the dish for 3-4 min. You will be able to tell when the silver coating is complete.
  • Remove the penny, rinse it, and blot dry with paper towels. (Do not rub.) Remove particles of zinc.
  • Using crucible tongs or tweezers, place the coated penny on the hot plate. The gold color appears immediately.
  • When the gold color forms, remove the coin, rinse it, and dry it with paper towels.
  • Special disposal procedures: Do not discard the waste zinc in the trash container. When zinc dries, it forms a powder that may spontaneously ignite. Rinse the NaOH-zinc mixture several times with water. Then add the solid to a beaker that contains 200 mL of 1 M H 2 SO 4 size 12{H rSub { size 8{2} } "SO" rSub { size 8{4} } } {} . When all of the solid dissolves, flush the zinc sulfate solution down the drain.

 Example of the calculation of molar mass:

  • Graph the electric current (in amps) on the y-axis against time (in seconds) on the x-axis. The total charge that passed through the electrolysis cell is given by the area beneath this curve. If the current is constant, this area is:

Q = area = I × t size 12{Q="area"=I times t} {}

Calculate this charge in coulombs.

  • Convert the coulombs of charge to mol electrons: 

N =

  The equation for the reduction half-reaction responsible for the plating at the cathode is

Cu 2 + ( aq ) + 2e Cu ( s ) size 12{"Cu" rSup { size 8{2+{}} } \( "aq" \) +"2e" rSup { size 8{ - {}} } rightarrow "Cu" \( s \) } {}

 Use the mol ratios of the preceding balanced equation to calculate the number of moles of Cu plated out:

n ( Cu ) = n/2 size 12{n \( "Cu" \) ="n/2"} {}  

  • Use the initial and final weighings of the copper mesh electrode to calculate the mass of copper plated out:

m(Cu) = m(final)–m(initial)

  • Calculate the molar mass (M) of copper: 

M =

Electrochemistry pre-lab exercise

Hopefully here for the Pre-Lab

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

This assignment must be completed individually and turned in to your TA at the beginning of lab. You will not be allowed to begin the lab until you have completed this assignment.

1. Write a balanced chemical equation for the electrolysis of molten potassium iodide (KI).

 

 

2. An electric current of 0.211 mA passes through an electrolytic cell for 2.00 min. How many moles of electrons have passed through the cell?

 

 

 

 

3. A voltage drop of 3.412 V is measured across a resistance of 10.51 ohms. How much current is flowing through the resistor?

 

 

 

 

 

4. Why is the anode not weighed before electrolysis begins?

 

Report form: electrochemistry

Hopefully here for the Report Form

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

Initial mass of cathode ___________________g

Final mass of cathode ___________________g

Mass of copper plated out ___________________g

Time (min) Voltage (V) Current (A)
5
10
15
20
25
30
35
40
45
50
55
60

Show calculations for full credit!

Average Current = (A)

Total charge through cell ______________C

Number of moles e size 12{e rSup { size 8{ - {}} } } {} through cell ______________mol

Molar mass of copper ______________g/mol

Questions: 

1. What is oxidized and what is reduced when electroplating copper?

2. Write the half reactions that occur at the anode and electrode.

3. Why is it important not to touch the cleaned cathode?

 

 

4. What is the purpose of KNO 3 size 12{"KNO" rSub { size 8{3} } } {} in this experiment?

 

 

5. How would your results for the molar mass of copper be affected if hydrogen gas were also observed at the cathode?

 

 

6. What part of this procedure limits the accuracy of the molar mass determination?

 

Alchemy - copper into gold

  • Is this reaction an oxidation-reduction reaction?

 

 

  •  Why did the penny turn "silver"?

 

 

  • Why did it turn "gold"?

 

 

  • Why did we heat the penny to turn it "gold"? 

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Gen chem lab. OpenStax CNX. Oct 12, 2009 Download for free at http://cnx.org/content/col10452/1.51
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