# 0.9 Electrochemistry/alchemy: molar mass of cu and turning cu into  (Page 4/4)

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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 ${H}_{2}{\text{SO}}_{4}$ . 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:

$Q=\text{area}=I×t$

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

${\text{Cu}}^{2+}\left(\text{aq}\right)+{\text{2e}}^{-}\to \text{Cu}\left(s\right)$

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

$n\left(\text{Cu}\right)=\text{n/2}$

• 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 ${e}^{-}$ 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 ${\text{KNO}}_{3}$ 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"?

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
how did you get the value of 2000N.What calculations are needed to arrive at it
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