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topic 4134 p.1 of 2

Why does copper sulphate induce a kind of rust on a nail?


A discussion started in 1999 but continuing through 2019

1999

Q. Hello.

I'm doing a project and I was wondering if anybody could tell me what the chemical for copper sulphate is, and why it (induces) rust so quickly, if any one knows the answers to these questions, please feel free to tell me here! :) Thank you.

Oh yes, this is semi-urgent so if you have an answer please tell me now. ;)

Courtney S [last name deleted for privacy by Editor]
- Trenton Ontario, Canada


1999

A. Hi, Courtney. Actually, the chemical for copper sulfate [linked by editor to product info at Amazon] is called copper sulphate; it is usually found as blue copper sulphate pentahydrate crystals (sometimes available in pool supply stores), and the chemical formula for that is CuSO4·5H2O. Those crystals can be dissolved in water or diluted sulphuric acid and then it will make a blue solution of copper sulphate.

To my knowledge it does not cause a nail to rust, but copper metal does plate out onto the nail, and copper is sort of an orange-ish color that could perhaps be mistaken for rust. If you tell us what grade you are in we can try a grade-appropriate answer (by which I mean that if you are a high school senior, we do no favor to your education by talking babytalk; but there may be little point in esoteric chemistry terminology if you are in grade school, years away from studying chemistry nomenclature). Good luck!

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


2005

Copper sulphate rusts really quickly because when oxygen is interfered sulfate it causes a chemical reaction. This chemical reaction causes anything to rust in minutes or even hours. Copper's sulphate chemical properties are that it reacts to oxygen and once the oxygen reacts it eats away the copper sulphate metal.

Sincerely,

Yevgeny Shnaper
- Toronto, Ontario, Canada


2005

Congratulations to Mr Mooney on his patience when answering these questions - I'd just like to add a less misleading answer to this question than that provided by Mr Shnaper.

A. The "rust" on the nail is probably a powdery coating of metallic copper (which looks a rusty reddish brown), the copper ions come out of solution, oxidising the metallic iron atoms to make them into iron ions which dissolve. The "oxidising" here means a transfer of electrons (the copper ions are "reduced" at the same time). Copper II sulphate doesn't react too easily with oxygen as stated, it's already so "oxidised" that it can in fact "oxidise" the iron metal.
I use this resource occasionally to clear up queries on metal finishing chemistry and generally trust what I read here, so I guess most people would, and hate to think of them being so misled.

Ray Hicks
- Cambridge, U.K.



What do electrons have to do with it?

2006

Q. I'm a student in eighth grade working on a school science project in immersion copper plating and need to find out what is happening when the copper moves to the nail. My teacher said I need to describe it through a chemical equation. I am completely at a loss of how to find this out. Could you help me?

Peter [last name deleted for privacy by Editor]
student eighth grade - Hillsborough, California


2006

A. Hi Peter. The copper is dissolved in the watery solution as copper ions, which are blue, and they plate out onto the nail as copper metal, which is sort of orange. I'm surprised that an 8th-grader has the chemistry vocabulary to be able to understand such a reaction as a chemical formula, but it would be approximately like this:

Fe0 + Cu++SO4-- => Cu0 + Fe++SO4- -

Copper (Cu) is more electrochemically noble than iron (Fe) so it will displace iron from the surface, i.e., cause iron metal to dissolve into the solution so it (copper) can come out as a metal. Another way to look at this is that when metals have enough electrons they appear as the familiar metallic form, but when they don't have enough electrons they appear as soluble positively charged ions dissolved in solution. When iron and copper fight over the necessary electrons to balance their positive charges, and be reduced to metal rather than being ions, copper always wins. Copper exerts this more powerful pull on electrons due to nuclear physics principles that I can't quite explain because it is beyond my grade level. Good luck!

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


February 22, 2009 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I have to write a lab report on this experiment...how the copper in the copper sulfate solution transfers to the iron ... why does it do this? (anything to do with electrons ... I'm in high school so a more in depth answer is fine)

Campbell F [last name deleted for privacy by Editor]
student - New York, New York


So You Have to do a Science Fair Project
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or

February 28, 2009

A. Hi, Campbell. The paper clip is zinc plated steel. Just as salt or sugar will dissolve into solution up to an equilibrium point, metals will dissolve as well. So ionized copper will be in solution from the copper sulphate, and ionized zinc will go into solution from the coating on the paper clip.

Copper is more noble than zinc, meaning that when the two metals are available in this way, the copper has a stronger affinity for becoming/staying in metallic form (i.e., to grab or hold onto its electrons so it is not oxidized). So zinc will dissolve into the solution and copper will deposit out as metal on the paper clip until the paper clip is completely covered with copper. Once it is covered with copper metal and no more zinc is exposed, the reaction is finished. To learn more, read up on the "galvanic series" and the "seawater series". Best of luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



2006

Q. I am in fourth grade and I am doing the vinegar/salt with pennies copper coating a paper clip and I can't figure out what the scientific question should be for my science fair presentation.
Could it be:
Will vinegar and pennies copper coat a metal paper clip?

Madison H [last name deleted for privacy by Editor]
student - Ponte Vedra, Florida


2006

A. Hello, Madison. I think your question is excellent for a fourth grade project! Good luck!

Ted Mooney, finishing.com
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Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


2006

Q. Hi, I'm in 8th grade and I am doing a lab report but need to finish my analysis and can't figure out where the copper on the nails surface comes from?

This is urgent please respond quickly. Thank you

Julia [last name deleted for privacy by Editor]
student - Toronto, Ontario


2006

A. Assuming you dipped your nail into copper sulphate, the copper came from the copper sulphate, Julia. The copper is dissolved as copper ions in the blue copper sulphate, but deposits out as orange copper metal. Although copper metal is orange, copper ions are blue.

Ted Mooney, finishing.com
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Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



Everything Kids Science
from Abe Books

or

Q. I am doing a chemistry lab, and for each reaction I need to provide a balanced equation.
The reactions are:
1. bare copper wire on a hottest part of a flame held for a few minutes.
2. a nail on a test tube of the solution copper(II) sulfate
3. solid copper (II) sulfate pentahydrate over heat
4. same as number three, but then adding few drops of water
5. calcium chloride solution and sodium carbonate solution
6. mossy zinc on a test tube with hydrochloric acid solution

Monica S [last name deleted for privacy by Editor]


A. Hi, Monica. Your teacher sent me a note:

"Dear Mr. Mooney: Please just tell Monica to do her own homework!!"

Here's what I wrote back:

"I understand what you are trying to tell us, professor, and if Monica simply pastes her homework questions here and leaves it at that, we'll do as you ask and not post any answers. But if she attempts the work, we'll try to help her over any points of confusion."

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



December 4, 2008

Q. Hi I'm in Chemistry and one of the assignments is to figure out what you would add to a brand new shiny copper Aladdin genie lamp to make it appear as if it were a thousand years old. Obviously I would rust it, but I can't think of a creative way of rusting it, that would actually work. If I added HCl all over it would it work? What would make this lamp rust? Please help, thank you.

Jackie O [last name deleted for privacy by Editor]
student - Salem, Massachusetts


December 2008

A. Hi, Jackie. Only the corrosion products of iron may properly be called rust. So you can't actually make a copper lamp "rust" because rust is iron oxide, and you can't make iron oxide from copper; it's not actually correct to call the corrosion products of copper 'rust'.

Something to think about is what would a thousand year old copper lamp actually look like? Would it be brown like an old penny or green like the statue of liberty? I'd go with green. I'm guessing that your teacher will expect you to try to answer that question and explain your choice.

About adding HCl, hydrochloric acid (only appropriate for high school students supervised by the science teacher). Actually HCl doesn't dissolve copper, it dissolves copper oxides. So the result is that it would make the lamp brighter if it had begun to tarnish. However, if you spritz the copper with HCl (preferably, use vinegar and salt because it's much safer) and let it dry, the copper / copper oxide that it had dissolved into the solution can't remain in solution because there will be no solution left after it evaporates. So the formerly dissolved copper would become sort of a corroded coating on the lamp. Think it all through and earn an "A". Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


August 27, 2010

Q. Hello!

I am in the tenth grade, and my chemistry class recently did a nail lab. I'm having trouble finishing my summary, and I was wondering if you could help me. We put a nail, a small spoonful of salt, some copper sulfate crystals, and water in a plastic cup. We observed this mixture for three days. I see a lot of shiny, copper-colored clumps in the cup (possibly rust), but I'm not sure what it is. My teacher wants to know what I think is happening to the nail. What I'm wondering is what really is happening? Can you help me? Thank you!

Rachel S [last name deleted for privacy by Editor]
Student - Nashville,Tennessee


August 30, 2010

A. Hi, Rachel.

You didn't describe anything appearing to be happening to the nail, and are asking us to guess what is happening without even the benefit of what it looks like. But what is probably happening at the core of it all is Cu++ + Fe0 => Cu0 + Fe++, with the Cu being the shiny copper color lumps you see. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



November 27, 2010

Q. I also have this question, I'm really bad at chem and don't understand this experiment, what happens to the salt/ sodium chloride in your equation? CU++ + FE0? I understand that rust is forming but I don't get how. Thank you.

Sana R [last name deleted for privacy by Editor]
- Chicago, Illinois, United States


November 28, 2010

A. Hi, Sana.

You say that you're "really bad at chem", so please take this as a kindly suggestion that may help, rather than as stodgy nitpicking, but proper capitalization is essential to chemistry; you can't get passable until you pay attention to capitalization. You're asking what happens when a carbon-uranium compound reacts with a fluorine-europium compound :-)

You surely meant Cu (copper) and Fe (iron) . . .

No, rust is not forming, Sana. Copper is plating out onto the iron. Dissolved copper ions (Cu++) react with iron metal (Fe0) to form copper metal (Cu0) and dissolved iron ions (Fe++). The salt / sodium chloride is an agent that helps the conductivity and corrosion but isn't really participating in the reaction very much, but to some degree there is probably a little bit of
2Na+Cl- + Fe++SO4- - <=> Na+2+SO4- - + Fe++Cl2 going on there :-)

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


November 29, 2010

thumbs up signTHANK YOU! I kind of got it and got it right on the homework! Thank you so much!

Sana R [returning]
- Chicago, Illinois, United States



September 15, 2011

Q. When iron nail is dipped in copper sulphate solution, the copper gets deposited on which part of nail first.

Ritu M [last name deleted for privacy by Editor]
student - Noida, UP, India


September 15, 2011

A. Hi, Ritu.

Please submit a sketch of where you saw the copper deposited first if you are having trouble giving it a name, and we will tell you whether it's called the point, the head, the shank, or whatever :-) Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


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