Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: Jaques on March 31, 2006, 12:41:25 PM
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hehe.
Melting .(Correction not melting. but dissolving.) again. Only this time Its actually happening.
No idea what brought this on, but I wanted to try melting the hard shell out of eggs. And I've been successful until now.
So I thought if it were possible to get rid of the shell by using only household material, and well seems like it is. I took a normal egg and put it in a glass cup with Vinegar (acetic acid 5-15%) and Lemon juice (citric acid) mix. The mix was mostly Vinegar, and well for the first few minutes nothing much was happening. But then It started fizzing and well smelling really "ughh". And the reaction continued for awhile actually. like 2 days and 1 night. And well the fizz wasn't exactly normal, it was all sticky and stuff. Kinda funky. But by then the vinegar had diffused into the egg, since now the egg had a yellow-ish hue to it. But that didnt' allow me to see the yolk, which would assure me that the shell was complelty gone and only the transparant membrane is there holding the egg. So now I'm diffusing the egg with water, hopefully that'll work.
But I just checked if I could see the yolk, and I can, but i have to put it up against light. So If anyone has any idea on how to make the yolk visible, I'm willing to try it.
And I have a question for you. I'm still in highschool chemistry, so this kinda puzzles me. Acid and acid don't react right? If so then, how come there was fizz? Logically I assumed that the acids were reacting with the eggshell, and if that is true. Then what would be the chemical equation for this reaction? Just wondering and trying to make this an "academic" experiment.
Okay now for the picture.
What you see in the picture is the midway point. I'll take a more recent picture soon. Hopefully showing the yolk.
And yeah, it is floating. But i don't think it's floating because of the egg getting lighter in density or the water . You see the little bumps on the egg? Those are little packs of air, and that was a result of the reaction, and it rose up like that. And for the whole day and night it stayed up, but by the second evening it went down, which is when i changed it from vinegar to water. And right now it is sitting in water. [
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but I wanted to try melting the hard shell out of eggs
Dissolving, not melting.
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An egg shell is like 95% Calcium Carbonate (CaCO3). The rest is calcium phosphate, magnesium carbonate, and proteins.
http://antoine.frostburg.edu/chem/senese/101/consumer/faq/eggshell-composition.shtml
CaCO3 is commonly used as an antacid. I wish I could tell you what the reaction was, but I don't know what the products are. I'm not very well educated in Organic Chemistry. Hopefully one of our Organic Chemists will read your question. I can tell you the gas that is being released is CO2 though.
Also Borek is right. It's dissolve not melt.
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A bit more info:
When you submerge an egg in vinegar, the shell dissolves. Vinegar contains acetic acid, which breaks apart the solid calcium carbonate crystals that make up the eggshell into their calcium and carbonate parts. The calcium ions float free, while the carbonate goes to make carbon dioxide—the bubbles that you see.
Joe
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So what happens to the organic acid (acetic acid)?
Is it just a catalyst from the decomposition of CaCO3? Or does it get consumed?
Sorry I don't have much experience with Organic Chemistry.
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So what happens to the organic acid (acetic acid)?
Is it just a catalyst from the decomposition of CaCO3? Or does it get consumed?
Sorry I don't have much experience with Organic Chemistry.
What will happen if you use strong mineral acid instead of acetic acid?
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OOO. Sorry. Now that I know the Ca will be left over the balanced equation should look like this:
4CaCO3 + CH3COOH -> 2H2O + 4Ca + 6CO2
Am I right. Like I've said before, I haven't done much work with Organic Chemistry as far as expirements and education.
I do know though that excessive C2H6O + person -> funny behavior + tipsy person. ;)
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OOO. Sorry. Now that I know the Ca will be left over the balanced equation should look like this:
4CaCO3 + CH3COOH -> 2H2O + 4Ca + 6CO2
No. Please answer my question on strong mineral acids. Try with hydrochloric, as that's the simplest case.
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The acid will be consumed in the reaction. Hydrochloric acid + Calcium Carbonate would look like:
2HCl + CaCO3 -> CaCl2 + CO2 + H2O
The calcium would become calcium chloride. The left over H's, C's, and O's would become H2O and CO2.
This is what would happen if you used a mineral acid, right?
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2HCl + CaCO3 -> CaCl2 + CO2 + H2O
OK. Organic acids in this case will behave the same way - they are acids first, organic later :) Now try to write reaction of CaCO3 dissolving in acetic acid - all you have to do is to replace hydrochloric with acetic.
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5CH3COOH + 4CaCO3 -> 10H2O + 4CaC2 + 6CO2
I get stuck on the products. I'm not sure if it's CaC2 or just Ca. Joeflsts says that Ca just floats away free, unless he's not looking at the full reaction. ???
I intended to ask about organic acids and how they react with bases awhile ago. I guess I'm asking it now.
Thanks for helping me on this Borek by the way.
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5CH3COOH + 4CaCO3 -> 10H2O + 4CaC2 + 6CO2
Too complicated (and wrong)!!! Actually, the same reation takes place only that calcium acetate forms instead of calcium chloride. Nothing happens to the acetate ion. This is no redox reaction! :)
Hint: write "HAc" instead of CH3COOH (Where "Ac- stands for the acetate ion (CH3COO-))
I'm not sure if it's CaC2 or just Ca
Neither CaC2 nor Ca. The product is calcium acetate (CH3COO)2Ca
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Where "Ac- stands for the acetate ion (CH3COO-)
I thought I have seen Ac used to refer, not to CH3COO (like you said, and which makes sense to me), but instead to CH3CO, so acetates are, e.g., HOAc. I'm thus a little confused by what is meant by 'Ac' when I read it somewhere.
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Yes! Ac can stand either for an acetyl group (CH3CO) or for the acetate anion (CH3COO-)
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Sometimes CH3COO- is written as AcO- and acetic acid as AcOH.
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Wow...so this is organic chem? awhole lot different than hs chem.. That's for sure.
Well its gonna take some time for me to absorb and understand this . :o
but wow, thanks. I think i have a better understanding of the reaction! Now to learn the scientific part.
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Yea, I realized a long time ago organic chem is pretty in depth. I understand now. Thank you everyone I understand now. Borek and Alberto_Kravina, I've given you both scooby snacks for helping me to understand organic acids better.
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http://www.exploratorium.edu/cooking/eggs/eggcomposition.html
http://www.enchantedlearning.com/subjects/birds/label/chickenegg/answers.shtml
http://www.oeuf.ca/en/encyclopedie/oeufnatomie/
I wonder what other parts of the egg acetic acid react with
http://en.wikipedia.org/wiki/Calcium_carbonate
http://en.wikipedia.org/wiki/Acetic_acid
Is the combining of Calcium carbonate and Acetic acid considered a weak base - weak acid reaction?
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You all seemed to have left out the generation of oxygen in this reaction. Oxygen must have been generated as well as carbon dioxide, since the only way the chemical reaction could be balanced involves oxygen:
2Ca(CO)3 + 4CH3COOH --> 2Ca(COCH3)2 + 4CO2 + 2H20 + 3O2
By the way, acetic acid is denoted: HOAc, not HAc; Ac denotes O=CCH3
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by
Ac denotes O=CCH3
I meant the CH3CO-, I'm sure it could also be used to denote the CH3COO-
but acetic acid is more commonly denoted as HOAc in journals and articles. Sorry, I'm just picky :P
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I meant the CH3CO-, acetic acid is more commonly denoted as HOAc in journals and articles.
I would like to think that Ac always means the same thing in regards to 'acetate'. HOAc for acetic acid is what I have noticed most often. It is bad enough that another element already has that symbol. Is there an official meaning to 'Ac' in chemistry? (Other than actinium!)
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k1027iwi
Since you are being the picky point person could you answer my question?
Is the combining of Calcium carbonate and Acetic acid considered a weak base - weak acid reaction?
[end quote]
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billnotgatez.
Yes, this reaction would be considered a weak acid - weak base reaction, considering that the pH of calcium carbonate is about pH 8, which is pretty weak.
btw, before anyone catches my idiocy with the equation, I realized I made a mistake:
2 CH3COOH(aq) + CaCO3(s) --> Ca+2(aq) + CO2(g) + 2 CH3COO-(aq) + H2O(l)
There. Now we're all happy ;)
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the pH of calcium carbonate is about pH 8, which is pretty weak.
Can you elaborate on what you mean?
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Ksp CaCO3 [2.8 10-9]. Pretty insoluble salt, I wonder how you calculated the pH...
Maybe you meant the pH of calcium acetate, but also in this case you have to know the concentration..
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Alberto_Kravina
Do you consider the reaction between Calcium carbonate and Acetic acid a weak base - weak acid reaction?
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Yeah...acetic acid is a pretty weak acid (pKa=4,75), carbonate anion (which is the base in this case) is a medium-strong base (since it is the conjugated base of carbonic acid). The carbonate anion is not such a weak base, though....
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Problem with carbonic acid is that it is probably stronger than we think, just the Ka we observe is influenced by the H2O + CO2 <-> H2CO3 equilibrium - as it is moved to the left real concentration of H2CO3 is much lower than used in Ka expression.