Heat of Formation for Ammonium chloride

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SUMMARY

The heat of formation for ammonium chloride (NH4Cl) can be calculated using Hess's Law, which involves summing the heats of reaction for ammonia (NH3) and hydrochloric acid (HCl). The calculated heat of formation for the reaction between gaseous ammonia and hydrochloric acid is -247.7 kJ/mol. To arrive at the correct heat of formation, one must add the heats of formation and the aqueous heats of solution for both ammonia and hydrogen chloride.

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  • Basic skills in calculating enthalpy changes
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Homework Statement



The problem statement is to find the heat of formation of NH4CL using the calculated variables and two more reactions.
If I calculated it correctly the HF for ammonia plus hydrochloric acid to be -247.7kj/mol. I am not sure what else it is that I need to do.


Homework Equations



I am not sure how I am supposed to calculate delta H to begin with, I think that's where my problems are laying at the moment.

The Attempt at a Solution

 
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Ok I think I figured out what you did. It looks like you just added the heats of formation and aqueous heats of solution for ammonia and hydrogen chloride to get that number. What you need to do is use Hess’s Law: find the heat of reaction between gaseous ammonia and hydrogen chloride and then add these to the heats of formation of the reagents. This should give the correct answer.
 

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