# Calorimetery Problem. It's not a homework but I can't get the answer.

1. Nov 17, 2009

### Owelode

Calorimetery Problem. :( It's not a homework but I can't get the answer.

0.510 g of ethanol is burned in a flame calorimeter (constant pressure) containing 1200 g of water. The water is initially 22.46 C and is warmed up to 25.52 C as a result of the reaction. The heat capacity of the calorimeter is 10.4 kJ/ C. What is the change in enthaply for the combustion of ethanol? Also, calculate the heat released when 73.5 g of ethanol undergoes combustion.

2. Nov 17, 2009

### pzona

Re: Calorimetery Problem. :( It's not a homework but I can't get the answer.

Show an attempt at a solution? Relevant equations? Anything?

3. Nov 17, 2009

### Owelode

Re: Calorimetery Problem. :( It's not a homework but I can't get the answer.

I did attempt it on my own. I was hoping someone would explain it to me though.

I used Q(rxn) = Q(water) + Q(calorimeter)

Also expanded: Q (rxn) = -[(m*s*change in temp.) + (C*change in temp.)]
= -[(1200*4.184*3.06) + (10400*3.06)] <---- I changed things from joules to kJ

And then I am lost from there. I got 47.22 KJ

4. Nov 18, 2009

### Staff: Mentor

Re: Calorimetery Problem. :( It's not a homework but I can't get the answer.

Seems to me so far you are doing fine. 47.22kJ per how much ethanol? It will be better to list it either per gram or - even better - per mole. And watch the sign.

--

5. Nov 18, 2009

### pzona

Re: Calorimetery Problem. :( It's not a homework but I can't get the answer.

Your solution looks good so far, you're almost there. What equations do you know that include enthalpy and energy?