[julcae87]

How would I solve this?

Consider a calorimeter working at constant pressure.  The combustion of 1 g of benzene (MW=78.1134 g/mol), for which we know that deltaHBenzeneӨ = -3268 kJ/mol, raises the temperature by 26ºC.  Combustion of 2 g of urea (MW=60.0554 g/mol) raises the temperature by 13ºC.  What is the enthalpy of combustion of urea?


I thought delta H = qp since it is at constant pressure. But we don't have the heat capacity so how should I approach this question? Thanks!

[renge ishyo]

This is a two step problem. In step 1 (with benzene) the goal is to find the heat capacity of the calorimeter. You should use

 :delta: q = cm :delta: T, where  :delta: H = :delta: q

This first step gives you the heat capacity for the calorimeter, which is "c" in the above equation. You can then use this "c" with the urea data to calculation the  :delta: H for urea.

There are other steps if you want to be more precise, but I don't think those are applicable here 

[julcae87]

Thank you!