[Kody H]

I need help with a question for my homework that I know nothing about, I have read the guidelines and I now understand that you can not just hand me the answer. But I would love it if you helped me figure it out nonetheless, whether you see fit to just tell me the answer and explain how to work it out or simply hand me the working out and let myself figure it out I will be very happy with both outcomes.

Question: A coffee cup calorimeter initially contains 125g of water at a temperature of 24.2oC. When 10.5 g potassium bromide (KBr) is added to the water, the temperature becomes 21.1oC. Assume the specific heat capacity of the solution is 4.18JoC -1 g -1 and that no heat is transferred to the surroundings or to the calorimeter. What is the heat of solution (the heat created by the dissolving of the salt) of potassium bromide in kJ/mol?

Again, any help that will get myself further to our answer would be well appreciated.

Regards,
Kody

[Arkcon]

OK.  When you have absolutely no knowledge of how to salve a problem, you need to do two things -- understand the problem, and know how to solve it.  That's remarkably trite, I know, but it is a general overview of the steps.  So let's begin.

I going to assume you understand what's happening.  The temperature drops when you add KBr. You know how much, and how cold.  So you need to know the constant asked for.

Part two, you need a formula that relates all these.  A textbook, or failing that, a Google search, is what you need.  A quick search of the chemistry book's index, or of Google will give you the formula you need.

Write that formula down for us.  Then, write it again, this time, plugging in the numbers of what you know.  If there's only one unknown, solve for it.  If there's more then one, we'll have to do more work. But we'll at least have started.

And please stop telling us about your girlfriend, and how important it is to her future happiness to get a quick answer, and other things.  They don't add anything to the question.

[XeLa.]

Would it be fair to assume that if you're asking for chemistry help on your "girlfriend's behalf" wouldn't it be more pertinent for her to pose the questions on this forum personally along with her own attempt? Just a thought.

Also, like Arkcon said, identifying the proper equation to use is half the effort with stoichiometry.

KungKemi