# Homework Help: Calculating enthalpy of formation

1. Jul 26, 2011

### Lindsayyyy

Hi

1. The problem statement, all variables and given/known data
I shall calculate the enthalpy of formation of gaseous hydrogen chlorid at 298,15 K
with the usage of thw following data:

$$\Delta [NH_{3}+HCL ->NH_{4}] :-50,4 kJmol^{-1} \Delta H_{form} NH_{3}:-46,2kJmol^{-1} NHCL_{4}:-315kJmol^{-1}$$

and $$\Delta H_{solv} NH_{3}:-35,7kJmol^{-1} HCL:-73,5kJmol^{-1} NH_{4}CL:+16,4kJmol^{-1}$$

2. Relevant equations

I know that I need the formula that

$$\Delta H=\Sigma H(products) - \Sigma H(educts)$$

3. The attempt at a solution

Well to be honest I don't know where to start, our notes are just useless from the professor and I don't find anything useful on the internet. Would be nice if anyone could give me some hints.

Thanks for the help

2. Jul 30, 2011

### zaldar

the second list are all of those energies of solvation? What level of chemistry is this? You may need to look at Hess's law for this problem but usually you don't use energy of solvation in these...

Do you have an equation for the formation that you want to use..are they looking for HCl coming from hydrogen and chlorine only or from something else.