Homework Help: Chemistry

Posted by Abby on Thursday, June 21, 2012 at 6:56pm.

In the following experiment, a coffee-cup calorimeter containing 100. mL of H2O is used. The initial temperature of the calorimeter is 23.0 degrees C. If 3.80 g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution in the calorimeter? The heat of solution, Delta H, of CaCl_2 is -82.8 kJ/mol.

I found the answer -14.6 degrees C and it was not correct. I am not quite sure where my math went wrong.

Chemistry - DrBob222, Thursday, June 21, 2012 at 7:28pm
It would have helped if you had posted your work. That way I could find the error. As it is I'm slogging around in the dark. If CaCl2 is exothermic you know the temperature should go up and ot down.
3.80g/molar mass CaCl2 = mols.
mols CaCl2 x 82800 = ? Joules.
?J = mass H2O x specific heat H2O x (Tfinal-23.0) = 0 and solve for Tfinal.
Chemistry - Abby, Thursday, June 21, 2012 at 9:01pm
Thank you Dr Bob, I actually realized right after I posted the question I was not including the 100 g of H2O in my math.

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