# Homework Help: Enthalpy of reaction

1. Dec 9, 2012

### iRaid

1. The problem statement, all variables and given/known data
determine the change in enthalpy for the following reaction from the enthalpies of formation for the reactants and products. (C6H5OH -165 kJ/mol, CO2 -393.15 kJ/mol, H2O -285.83 kJ/mol)

2. Relevant equations

3. The attempt at a solution
No idea, been a while since I did this...if ever

Any direction is appreciated.

2. Dec 10, 2012

### mpreds

A change in enthalpy would indicate that there were parameters in the question that were changing. Do you have initial or final temperatures or any other data?

-Mark

3. Dec 10, 2012

### Staff: Mentor

4. Dec 11, 2012

### Telemachus

$\Delta H= \sum_i \nu_i \Delta H^0_{products}- \sum_j \nu_j\Delta H^0_{reactants}$

As Borek says, you should start by having the balanced chemical equation.

Last edited: Dec 11, 2012
5. Dec 15, 2012

### Staff: Mentor

As Borek said, you have to start out with a balanced reaction equation. But you do realize that there is a reactant missing from the problem statement? Ask yourself, what is it the C6H5OH has to be reacting with to produce CO2 and H2O? (hint: it's a combustion reaction). So, what is the missing reactant. The next thing you have to recall is that, if this reactant is an elementary substance, what is its heat of formation? How is the heat of reaction related to the heats of formation of the products and the reactants?