Combustion Equations [ENDORSED]

[Jessica Yang 1J]

For when we write out combustion equations and calculate enthalpy of combustion, do we treat the water in the products as a water or gas? (because I think the enthalpy of formation of water as a gas and water as a liquid is different)

[Vincent Tse 1K]

I think it's liquid water. At least, that's what I've mostly seen in the problems I've done. Have you found a problem that uses gaseous water for combustion?

[Sammy Thatipelli 1B]

In combustion, the product water would always be liquid. We know this because the phase of water is based on the temperature by which the reaction is occurring. Reactions occurring at the standard room temperature, 25 degrees C, will produce water as a liquid. This is the case for the combustion reactions we see in the book.

[Chem_Mod]

The above post is well explained. A small caveat is that the water will not always be liquid in a combustion.
However, as stated, combustion at standard state conditions will produce liquid water.

[AtreyiMitra2L]

The book says that water in the liquid form will be formed only with organic compounds. When it is not an organic compund, then gas will be formed.