[kclive]

my chem teacher gave us this worksheet to do over winter break. And i'm stumped on one of the problems . Here we go:

"When 5.50 g NH₄NO₃ is dissolved in 100 mL of water, the temperature of the water decreases from 21.5^oC to 18.3^oC. Calculate the molar heat of solution of ammonium nitrate."

What exactly is molar heat of solution ? I've looked thru my notes about 5 or 6 times and i cant even find it. Can you PLEEAAASSSEE help? The worksheet is due January 6^th, so you guys have plenty of time to figure this out .

Thanks!

[jdurg]

Molar Heat of Solution is the change in enthalpy when one mole of a substance is dissolved into solution.  So the question is asking you "What's the Delta H when you dissolved one mole of ammonium nitrate in water?".  To answer your question you'll need to know the following:

specific heat capacity of water  (You'll need to look this up).
the density of water  (Again, you'll need to look this up).
the volume of water you used  (100 mL).
the mass of ammonium nitrate you used  (5.50 g)
the molecular mass of ammonium nitrate  (You can calculate this;  2N, 4H, 3O)
the change in temperature.  (Tf - Ti;  18.3-21.5)

With this information, you will be able to easily figure it out.  

[kclive]

Hey I found this formula on a big formula sheet my teacher gave us. There is a value called C_p that is the "molar heat capacity at constant pressure." And the formula for finding it is ?H / ?T. I already know ?T, which is |18.3 - 21.5|, which is 3.2. Now I need help finding ?H....

I already know that the density of water is 1 g/mL, while the density is 4.184 (I dont know the units but thats not necessary here). And the molar mass of ammonium nitrate is of course, 80g (approximately; it is really 80.02g). But I dont really know how to find ?H.

All help is appreciated!

 :please: