Question

Question as follows:

If you combusted 23g of ethanol with an excess of oxygen how much heat would be released or absorbed?

the only thing I've deduced is the chemical reaction:

C2H6O + 302 -> 3H20 + 2C02

I'm not sure how to proceed. I need Q. Not sure which equation to use since there is no temperature. Am I to assume 298K?

Answer 1

No. You find the heat of combustion which is in tables (or you can calculate it), then
q = dHcombustion x (23g/molar mass ethanol)

If you don't have heat combustion tables you can calculate it this way. From your equation above, use
dHfrxn = dH combustion = (n*dHf products) - (n*dHf reactants). The heats of formation are in tables, too, usually in the appendix. CO2 is approx -393.5 kJ/mol (but I don't remember all of these so you must look them up) and H2O is about -285 kJ/mol or so. I don't have the foggiest about ethanol.