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Topic: Calcium Oxide Decomposition  (Read 33640 times)

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Offline Diamonds

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Calcium Oxide Decomposition
« on: March 10, 2013, 12:01:07 AM »
Why does CaO not decompose into Ca and O2? I have been looking all over the web and can't find an appropriate equation that represents or explains this. Thanks in advance!

Offline Adam2126

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Re: Calcium Oxide Decomposition
« Reply #1 on: March 10, 2013, 12:05:26 AM »
I'm new to chemistry but I think I may know what's going on.
There appears to be an equal number of moles on either side when CaO decomposes into Ca and O, so why would CaO decompose into Ca and O2? Naturally oxygen is found as O2, but this is a spontaneous reaction.

But perhaps you're referring to Ca^2+? That would look like Ca(O)2, though.. But then again, I'm not sure.

Offline Diamonds

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Re: Calcium Oxide Decomposition
« Reply #2 on: March 10, 2013, 12:56:59 AM »
Sorry for the misunderstanding. This isn't a stoichiometry question.

I would expect the reaction to be

2CaO  :rarrow:  2Ca + O2, but it is not so. I am asking a question about the actual reaction, not the coefficients.

Offline Borek

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Re: Calcium Oxide Decomposition
« Reply #3 on: March 10, 2013, 05:30:15 AM »
Why should it decompose in the first place, it is much more stable than the mixture of Ca and O2.
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Offline Arkcon

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Re: Calcium Oxide Decomposition
« Reply #4 on: March 10, 2013, 08:50:23 AM »
Why does CaO not decompose into Ca and O2?

Who says it doesn't?  Also, why should it?  As Borek: asked.  How easy did you need it decomposed?

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I have been looking all over the web


You should try harder.  http://en.wikipedia.org/wiki/Calcium#History

Quote
and can't find an appropriate equation that represents or explains this. Thanks in advance!
Since you wrote a balanced chemical equation for Adam2126:, I'm guessing you didn't mean this.  But what did you mean?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Big-Daddy

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Re: Calcium Oxide Decomposition
« Reply #5 on: March 10, 2013, 12:26:53 PM »
I am sure that, under enough heating, either CaO will liquify/sublime or will decompose into Ca and O. Probably the former, considering that oxides tend to form lattices with very high dissociation enthalpy.

But that's besides the main point. Most plain oxides do not decompose under Bunsen burner temperatures (around 1000 K).

Offline Arkcon

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Re: Calcium Oxide Decomposition
« Reply #6 on: March 10, 2013, 01:42:18 PM »
I am sure that, under enough heating, either CaO will liquify/sublime or will decompose into Ca and O. Probably the former, considering that oxides tend to form lattices with very high dissociation enthalpy.

A fair guess, Big-Daddy:, but for this specific case, not likely at any reasonable temperature.  http://en.wikipedia.org/wiki/Refractory#Refractory_materials

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But that's besides the main point. Most plain oxides do not decompose under Bunsen burner temperatures (around 1000 K).

Plain ones being the ones cited above, then, yeah.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Loael

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Re: Calcium Oxide Decomposition
« Reply #7 on: March 16, 2013, 04:30:46 PM »
I can tell you already the reaction is not 2CaO --> 2Ca + O2

Why may you ask? I actually took a practice Olympiad today and one of the questions asked which one does not form O2 when it decomposes? The answer was CaO.

The specific question was "Oxygen gas can be produced by the decomposition of all of the following substances EXCEPT:

A) Calcium oxide
B) Hydrogen peroxide
C) Mercury(II) Oxide
D) Ozone


The answer was A


But as others have said, Calcium Oxide will not decompose on its own. If anything it'll undergo hydration to form calcium hydroxide. But for a reason why it doesn't decompose into it, I'm not so sure.

Offline Borek

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Re: Calcium Oxide Decomposition
« Reply #8 on: March 16, 2013, 05:09:05 PM »
As it was signaled several times, it doesn't decompose because - for thermodynamical reasons - it is pretty stable.

Every substance will decompose if heated strong enough. But if something requires heating to very high temperature, products don't have to be these we know from the STP  - and for example at high temperatures oxygen dissociates to the atomic gas.
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Offline Needaask

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Re: Calcium Oxide Decomposition
« Reply #9 on: March 17, 2013, 04:05:52 AM »
As it was signaled several times, it doesn't decompose because - for thermodynamical reasons - it is pretty stable.

Every substance will decompose if heated strong enough. But if something requires heating to very high temperature, products don't have to be these we know from the STP  - and for example at high temperatures oxygen dissociates to the atomic gas.

Hi Borek, from this question I was thinking about decomposition and melting. Both involves the process of bond breaking but the former requires new bonds to be formed as well. So why do some compounds melt and others decompose? Or do some compounds melt then decompose? Then how does boiling come in since that's similar to lattice energy already?

Thanks so much :)

Offline Borek

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Re: Calcium Oxide Decomposition
« Reply #10 on: March 17, 2013, 06:06:21 AM »
Both involves the process of bond breaking but the former requires new bonds to be formed as well. So why do some compounds melt and others decompose? Or do some compounds melt then decompose? Then how does boiling come in since that's similar to lattice energy already?

Start with covalent compounds.

Which bonds break during melting?

Which bonds break during decomposition?

Which bonds break during boiling?

What may cause the compound to decompose before melting or boiling?
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Offline Needaask

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Re: Calcium Oxide Decomposition
« Reply #11 on: March 17, 2013, 09:08:31 AM »
Both involves the process of bond breaking but the former requires new bonds to be formed as well. So why do some compounds melt and others decompose? Or do some compounds melt then decompose? Then how does boiling come in since that's similar to lattice energy already?

Start with covalent compounds.

Which bonds break during melting?

Which bonds break during decomposition?

Which bonds break during boiling?

What may cause the compound to decompose before melting or boiling?

You mean for simple covalent molecules right?

1) some the intermolecular forces of attraction breaks
2) both the intermolecular forces (not sure if all breaks) and the actual bonds break?
3) all the intermolecular forces of attraction breaks
4) I would guess that if the compound's bond strength is weaker than the bond strength? But in all cases the bond strength is way stronger than any intermolecular forces of attraction so actually thinking about it now, when I boil water is any energy put in to start breaking those O-H bonds or is all the energy put to destroy those good interaction there?

Greatly appreciate the help :)

Offline Borek

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Re: Calcium Oxide Decomposition
« Reply #12 on: March 17, 2013, 09:27:39 AM »
bond strength is weaker than the bond strength?

Think in terms of INTERmolecular forces (bonds) and INTRAmolecular forces (bonds).
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Offline Needaask

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Re: Calcium Oxide Decomposition
« Reply #13 on: March 17, 2013, 10:32:55 AM »
bond strength is weaker than the bond strength?

Think in terms of INTERmolecular forces (bonds) and INTRAmolecular forces (bonds).

Oops sorry I meant to say the intramolecular forces (the actual covalent bonds) would have to be weaker than the intermolecular forces (van der waals forces). But then again that's impossible right?

Thanks again :)

Offline Borek

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Re: Calcium Oxide Decomposition
« Reply #14 on: March 17, 2013, 10:36:09 AM »
Have you ever seen heated sugar caramelizing?
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