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Topic: Amount of CO2 that goes into CaCO3  (Read 6508 times)

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chimpy

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Amount of CO2 that goes into CaCO3
« on: March 16, 2006, 12:27:51 PM »
OK, here's my problem:

I have two equations:

Number (1)

2CuCO3(s) ------> Cu2O(s) + 2CO2(g) + 1/2O2(g)

Number (2)

CuCO3(s) ------> CuO(s) + CO2(g)

I gotta setup an post-experiment to determine (using the volume of the CO2(g)) which equation has happened.

I thought that what I could do was get the volume of the CO2(g) by feeding off the reaction into a gas syringe, capturing all the gas, take a reading, then pump and bubble it through Ca(OH)2(l) (limewater).

What I'm wondering is: Is it possible to tell (by just using what I described above) which reaction that it is?
Take this scenario as an example of what I'm looking to happen.

I increase the amount of reactants in both reactions equally so that, a couple of moles of CO2(g) are given off in reaction (1) and, say, 1 mol given off in reaction (2). Ideally, in reaction (1) so much CO2(g) is given off that it precipitate is produced, then reacted again so that the solution goes clear again. And in reaction (2), that there is enough CO2(g) to only make the Ca(OH)2(l) stay white with the precipitate.

Therefore, it is clear which reaction has taken place, by just looking at the colour of the limewater.

So, what I need to know is (sorry that this is long-winded, but I wanted to make sure you understood what I needed) whether this is possible, amid the ambigousness AND what the threshholds (as in the specific amounts of CO2(g)) for when the Ca(OH)2(g) goes white, and then clear again.

THANK YOU VERY MUCH, YOU'VE BEEN A GREAT *delete me*!!  :happycrying:

N.B.

This is related to Planning part of Coursework. Please, if you do decide to help me, say only whether it would work, and what the threshholds would be. :) You won't get in trouble, but I could for getting too much help :)

Anywho, thanks a bunch,

Lewis.
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Re:Amount of CO2 that goes into CaCO3
« Reply #1 on: March 16, 2006, 12:47:26 PM »
Quote from: chimpy on March 16, 2006, 12:27:51 PM
Therefore, it is clear which reaction has taken place, by just looking at the colour of the limewater.

First you will have to be sure you are catching CO2 quantitatively. Second you will know nothing if both experiments end with the same result.

Intuition tells me you will have to use impractically large quantities of lime water for your method to work.
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Offline xiankai

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Re:Amount of CO2 that goes into CaCO3
« Reply #2 on: March 16, 2006, 07:56:38 PM »
i just realised that both reactions produce the same amount of CO2, so you cant possibly distinguish between the two judging on the amount of CO2 produced, its either that or the reaction number (1) is wrong.

was it a given guideline that the basis of your planning was to focus on the volume of CO2? i hope not, that constraints everything.
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Re:Amount of CO2 that goes into CaCO3
« Reply #3 on: March 16, 2006, 08:29:12 PM »
Quote from: xiankai on March 16, 2006, 07:56:38 PM
i just realised that both reactions produce the same amount of CO2.

Per 1g of copper carbonate?
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Offline xiankai

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Re:Amount of CO2 that goes into CaCO3
« Reply #4 on: March 17, 2006, 06:27:26 AM »
Quote from: Borek on March 16, 2006, 08:29:12 PM
Per 1g of copper carbonate?

according to his mole ratios...

(1) 2CuCO3 . 2CO2

(2) CuCO3 . CO2
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chimpy

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Re:Amount of CO2 that goes into CaCO3
« Reply #5 on: March 17, 2006, 08:14:01 AM »
Ah, crud. I see what you mean. Hmm, well, my coursework sheet doesn't specifically mention CO2, it just says "the volume of gas". So, I thought that meant if you wanted to tell the two reactions apart via gas alone and not the other physical end product, you had to use CO2, but now after what xiankai said, I suppose you have to find a way of identifying CO2 and O2 together (for equation (1)). Any suggestions?

Plus, surely, if I knew the threshhold at which Ca(OH)2 changed to CaCO3, then regardless that they gave off the same amounts of CO2, if I specified the grams of CuCO3 to be used, then the Ca(OH)2 would still hopefully go clear or cloudy right? They still  give off double the amount of the other!

One last point: On my coursework sheet, it notes that I should specify "what amounts of reactants are to be used" and "to use my knowledge of molar equations".
« Last Edit: March 17, 2006, 08:20:40 AM by chimpy »
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Re:Amount of CO2 that goes into CaCO3
« Reply #6 on: March 17, 2006, 09:22:24 AM »
Quote from: xiankai on March 17, 2006, 06:27:26 AM
according to his mole ratios...

(1) 2CuCO3 . 2CO2

(2) CuCO3 . CO2

Sorry, shouldn't answered at 2:30 am ;) You are right.
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