How Do You Calculate the Formation Reaction ΔH Using Hess's Law?

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SUMMARY

The discussion focuses on calculating the formation reaction ΔH using Hess's Law, specifically through the reactions involving NH4Cl(aq), NH3(aq), and HCl(aq). Participants were tasked with determining the neutralization reaction ΔH and solution reaction ΔH based on provided enthalpy values for specific reactions. The key reactions included the formation of NH3(g) from N2(g) and H2(g), and the formation of HCl(g) from H2(g) and Cl2(g). The final goal was to derive the formation reaction ΔH for NH4Cl(aq) using the calculated values.

PREREQUISITES
  • Understanding of Hess's Law and its application in thermochemistry
  • Familiarity with enthalpy changes and their calculations
  • Knowledge of chemical reaction equations and stoichiometry
  • Experience with aqueous solution chemistry and concentration calculations
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  • Study Hess's Law applications in various chemical reactions
  • Learn how to calculate enthalpy changes using standard enthalpy of formation
  • Explore the concept of neutralization reactions and their enthalpy changes
  • Review aqueous solution chemistry, focusing on molarity and its effects on reaction enthalpy
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Chemistry students, educators, and researchers interested in thermodynamics and reaction enthalpy calculations, particularly those studying Hess's Law and its practical applications in laboratory settings.

Race
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We studied the reactions NH4Cl(aq) → NH4(aq) + Cl (aq) and NH3(aq) + HCL (aq) → NH4Cl(aq) in lab today, and part of our assignment was to give the formation reaction by first calculating the neutralization part ΔH of our lab and the solution reaction part ΔH of our lab.

We were given this:

1/2N2(g) +3/2H2(g) → NH3(g) -45.77kj
1/2H2(g)+ 1/2Cl2(g) → HCl (g) -92.31kj
NH3(g) → NH3(aq. 1.50M) -35.40kj
HCl(g) → HCl(aq, 1.50M) -72.84 kj

And were asked to add the reactions we did in class to them. Then we were asked for Neutralization reaction ΔH and Solution reaction ΔH. After we found this we were asked for Formation reaction ΔH.


My attempt at a solution:

My lab partner did everything with the professor while I was cleaning up from the actual experiment, and they went to the office and since lab went over time I had to rush to get to work, so whatever was done I didn't get to see. So I'm trying to work through this on my own until my professor e-mails me back!

I have done several Hess's Law problems in the past, but was never as confused by the wording of the question as I am now. If someone could just figure that out, I would appreciate it so much!
 
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Probably the best starting point is to write reaction equations for both processes in question.
 

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