[Edher]

Saludos,

I know for sure this problem is going to be on my test tomorrow in the evening, so I really need your help to be able to ace it.

When 0.115 mole of NH4Cl(s) are dissolved in 750 (g) of water in a constant pressure calorimeter (the total heat capacity of the calorimeter is 3.88 kJ/*C), the temperature of the calorimeter decreased from 26.12*C to 24.28*C. What is ?H* for the solution of 1 mole of NH4Cl(s)?

      The thing that really throws me off here is that they don't give you the mass with the heat capacity. In other words, it isn't kJ/*C mole. In this problem it's simply kJ/*C. My concern is how am i going to get the mass to cancel?

      I'm kind of confused on how to approach this problem. I was thinking of first finding ?U by using this formula   ?U = q + w. And then use this other formula to find ?H.   ?H = ?U + P?V

Any tips,

Thank you,
Edher

[Borek]

You mean heat capacity of the calorimeter is not expressed in J/mol deg C?

This is not standard heat capacity, but heat capacity, so there is no need for mass or number of moles. Mass (nor number of moles) of the calorimeter usually doesn't change during experiment.