Combustion Analysis

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Miranda 1J
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Joined: Fri Sep 29, 2017 7:06 am

Combustion Analysis

Postby Miranda 1J » Thu Oct 05, 2017 9:46 pm

In a combustion analysis of an unknown compound do we always assume it only contains C, H, O ? How would we know if it contained something else too?

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Joined: Fri Sep 29, 2017 7:06 am
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Re: Combustion Analysis

Postby PranithaPrasad » Thu Oct 05, 2017 9:58 pm

Other elements can be involved in a combustion reaction. Usually it's that O2 is a reactant and the products must include CO2 and H2O. If there are other elements involved, we would be told in the problem.

Jessica Beroukhim 3K
Posts: 21
Joined: Fri Sep 29, 2017 7:07 am

Re: Combustion Analysis

Postby Jessica Beroukhim 3K » Thu Oct 05, 2017 10:00 pm

If it's combustion of a hydrocarbon it will be C and H for sure.
If you're given the products of the combustion you can assume that all the elements other than oxygen are for sure in the combusted substance. If the mass of all the elements other than oxygen in the products is less than the given mass of the reactant (the combusted substance) then the remaining mass of the reactant must be oxygen. You can look at the solution for M19 for an examples of this.

Clarissa Molina 1D
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Joined: Fri Sep 29, 2017 7:04 am

Re: Combustion Analysis

Postby Clarissa Molina 1D » Thu Oct 05, 2017 10:48 pm

Do C, H, and O all have to be present in order for it to be a combustion analysis problem, and will the problem state which elements are involved?

Peri Bingham 1G
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Joined: Fri Sep 29, 2017 7:03 am

Re: Combustion Analysis

Postby Peri Bingham 1G » Thu Oct 05, 2017 10:53 pm

The elements should be given in the problem. A good example of this kinda of in the textbook is problem M.19 in the fundamentals section. It indirectly lists which elements are in the sample based on the products of the reactions.

Diane Bui 2J
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Joined: Sat Jul 22, 2017 3:00 am

Re: Combustion Analysis

Postby Diane Bui 2J » Sat Oct 07, 2017 12:51 am

The problem will most likely state which elements are involved in the combustion, but combustion usually occurs when a hydrocarbon reacts in the presence of oxygen to produce carbon dioxide and water. Hence, the elements of C,H, and O are asked in the problem. Combustion/burning/oxidation of organic molecules is the same as oxidative metabolism: they all release energy.

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