Hi all,

 

I have been tasked with finding the equation for the combustion of heptane (C7H16).

 

We put some heptane on a watch glass and watched it burn and it disappeared. I am assuming that it reacted with the air, or the moisture in it. Does it evaporating rather quickly on the watch glass point to something obvious?

 

Can someone point me in the right direction?

 

All questions and comments are appreciated.

 

Thanks!

 

»fo

 

 

EDIT:

 

Something like this...???

 

C7H16 + 11(O2) == 7(CO2) + 8(H2O)

The reaction you wrote down is correct.

 

The heptane reacted with air, not with moisture. Actually, it reacted only with the oxygen (O2) from air. The other compounds in air, such as nitrogen (N2), don't do much. Moisture is a product from the reaction. Moisture (water) is H2O that is formed.

 

About the evaporation: when it burned it created heat. This heat made it evaporate faster. (It's like water: it evaporates a lot faster on a hot summer's day than in winter).

the Heat of the enthalpy change is enough to overcome the Van de walls forces keeping the individual molecules together.

 

so they "Evaporate".