[selk]

An unknown amount of KI was dissolved in 60.0 g of water in a calorimeter, the temperature dropped from 27.2°C to 13.2°C. Determine the mass of KI added to the calorimeter.

KI(s) → K(aq) + I(aq)    ΔH = 20.3 kJ

Please help I have a test tomorrow and my chem teacher doesn't even know how to solve this problem when I asked her, despite her giving us this problem as hw??

[Hunter2]

What about specific heat capacity.

[Borek]

As with every thermochemistry problem, first step is to write the heat balance - find out what "consumes" heat and what is the heat source.

And, as you were already told, this problem as stated doesn't have complete information. It is still easy to solve, as the missing information is a very basic property of water, one that you can safely get from tables.