Don H. Posted February 1, 2011 Share Posted February 1, 2011 (edited) Instant cold packs used to treat athletic injuries contain solid NH4NO3 and a pouch of water. When the pack is squeezed, the pouch breaks and the solid dissolves, lowering the temperature because of the following endothermic reaction. NH4NO3(s) + H2O(l) = NH4NO3(aq) deltaH = +25.7 kJ What is the final temperature in a squeezed cold pack that contains 50.0 g of NH4NO3 dissolved in 115 mL of water? Assume a specific heat of 4.18 J/(g·°C) for the solution, an initial temperature of 25.0°C, and no heat transfer between the cold pack and the environment. To find the mass of water use the density of water = 1.0 g/mL. Hint: The process takes place at constant pressure. So i know at constant pressure i have to use Cs * M of solution * deltaT = -(molesNH4NO3)*DeltaH of reaction Can someone please set this problem up because I tried to set it up but had difficulties with some of the values. Edited February 1, 2011 by Don H. Link to comment Share on other sites More sharing options...
Fuzzwood Posted February 1, 2011 Share Posted February 1, 2011 You have every value needed to find T2, which is T1 + deltaT. This is just a fill the numbers-exercise. Link to comment Share on other sites More sharing options...
Horza2002 Posted February 1, 2011 Share Posted February 1, 2011 You will also need to find out how many moles of NH4NO3 you are dissolving. Link to comment Share on other sites More sharing options...
Fuzzwood Posted February 1, 2011 Share Posted February 1, 2011 He has the mass of the ammonium nitrate. Not sure if the solubility of that stuff is 50g/115ml tho, you might want to check that Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now