H2O as a liquid or vapor

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Kathleen Vidanes 1E
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Joined: Fri Sep 29, 2017 7:07 am

H2O as a liquid or vapor

Postby Kathleen Vidanes 1E » Tue Jan 23, 2018 2:40 pm

Although this might not necessarily relate to thermochemistry, I was wondering when do we know whether to specify H2O as being a liquid or vapor within a balanced chemical reaction, specifically for combustion?

I was doing homework question 8.57 where we had to use Hess's law with multiple combustion balanced chemical reactions, and they all specified water as a liquid.

Grace Han 2K
Posts: 33
Joined: Tue Nov 15, 2016 3:00 am

Re: H2O as a liquid or vapor

Postby Grace Han 2K » Tue Jan 23, 2018 2:45 pm

I’m not sure if this is correct, but I think in general, for combustion, Hydrocarbons combust with oxygen to produce carbon dioxide and liquid water.

It would be great if someone could clarify!

Posts: 32
Joined: Thu Jul 27, 2017 3:00 am

Re: H2O as a liquid or vapor

Postby RyanS2J » Tue Jan 23, 2018 3:12 pm

Combustion can produce either liquid or vapor water, but in the case of the standard enthalpy of combustion (calculated under standard conditions), water is taken to be in liquid form.

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