## 8.93a Post-combustion, is the water a gas or liquid?

$w=-P\Delta V$
and
$w=-\int_{V_{1}}^{V_{2}}PdV=-nRTln\frac{V_{2}}{V_{1}}$

SubparChemist
Posts: 27
Joined: Fri Sep 25, 2015 3:00 am

### 8.93a Post-combustion, is the water a gas or liquid?

When the equation is not given, as in problem 8.93, how do we determine whether the resulting water product of a combustion reaction is a vapor or a liquid? Sometimes I'll see it written as a gas and other times I'll see it written as a liquid.

"Calculate the work that must be done against the atmosphere for the expansion fo the gaseous products in the combustion of 1.00 mol C6H6 (l) at 25 degrees Celsius and 1.00 bar"

I wrote down C6H6 (l) + 15/2*O2 (g) -> 6*CO2 (g) + 3*H2O (g), but according to the solutions manual, the H2O is actually a liquid at the end of this reaction.

Chem_Mod
Posts: 18910
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 737 times

### Re: 8.93a Post-combustion, is the water a gas or liquid?

The solution manual may vary, but generally you can assume the product is a gas.

SubparChemist
Posts: 27
Joined: Fri Sep 25, 2015 3:00 am

### Re: 8.93a Post-combustion, is the water a gas or liquid?

Update:

Asked my TA, Dan, and Dr. Lavelle, both informed me it depends on the temperature at which the reaction occurs. Since this combustion was at 25 degrees Celsius, water would be a liquid as a product. Had it occurred at 100 degrees Celsius or higher, it would've been a gas.