## Help With Question 8.39 [ENDORSED]

Simone Seliger 1C
Posts: 30
Joined: Fri Sep 25, 2015 3:00 am

### Help With Question 8.39

What is the value 6.01 kJ.mol^-1 representing in this answer? It has the same units as Gibbs free energy, but when I looked in the index that value for H20 was way different. Shouldn't it be the heat constant for that molecule? And where can we find that value in the textbook?

Thanks!

Christopher Reed 1H
Posts: 33
Joined: Wed Sep 21, 2016 2:57 pm
Been upvoted: 1 time

### Re: Help With Question 8.39  [ENDORSED]

Hello!

The value of 6.01 kJ/mol is the enthalpy of fusion for water. I would not concern yourself with Gibbs Free Energy at the moment.

You need to use the enthalpy of fusion because your starting sample is ICE and you want your final to be a LIQUID. In other words, the enthalpy of fusion is for when you are considering the phase change (temperature does not change!) from solid water to liquid water.

You would use the heat capacity of LIQUID WATER to find how much energy it would take to raise the sample to 20 degrees Celsius.

In summary:

$\Delta H=\Delta H_{fus}*n$ will give you the energy needed to change ice at 0 degrees Celsius to liquid at 0 degrees Celsius. The variable n here represents moles.
$\Delta H=m\Delta TC$ will tell you the energy needed to raise the temperature of liquid water by X degrees Celsius. The variable C represents the specific heat capacity of liquid water.

Simone Seliger 1C
Posts: 30
Joined: Fri Sep 25, 2015 3:00 am

### Re: Help With Question 8.39

Ok, thanks so much.

I was confused because in my discussion my TA gave us a different value for enthalpy of fusion that we used in an example for water. It was 334 J/mol.