Heat of Reaction Experiment, High school level

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SUMMARY

The discussion centers on the heat of reaction in the neutralization of hydrochloric acid (HCl) and sodium hydroxide (NaOH), specifically addressing the exothermic nature of the reaction despite the initial energy absorption during dissociation. Participants concluded that the formation of water from the ions is a more stable state, which releases energy into the environment, resulting in an observable temperature increase. The key takeaway is that the energy released during the formation of water outweighs the energy absorbed during the dissociation of NaOH, leading to an overall exothermic reaction.

PREREQUISITES
  • Understanding of acid-base reactions
  • Knowledge of exothermic and endothermic processes
  • Familiarity with ionic dissociation
  • Basic principles of thermodynamics in chemistry
NEXT STEPS
  • Study the principles of exothermic reactions in detail
  • Learn about the enthalpy changes in neutralization reactions
  • Explore the concept of ionic stability and solvation
  • Investigate the thermodynamic properties of water formation
USEFUL FOR

This discussion is beneficial for high school chemistry students, educators teaching acid-base chemistry, and anyone interested in understanding thermodynamic principles in chemical reactions.

bethanyd
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Homework Statement
I am working on a correspondence grade 12 Chemistry Course and I am confused by one question. I did an experiment involving hydrochloric acid (HCl) and sodium hydroxide (NaOH). Here is the question:
"In a reaction, Na+ ions are separated from OH- ions, a process of dissociation that absorbs energy, yet, in the end, heat was liberated by the overall process. Explain."

This has been asked before on this forum but there was not really a clear answer posted so I thought perhaps we could discuss it again. Here is the archived thread: https://www.physicsforums.com/archive/index.php/t-77030.html

The attempt at a solution
So I understand that, since the reaction was exothermic, something other than the breaking of the NaOH bonds must have occurred which took less energy and thus released the excess energy in the form of heat. I do not quite understand what happened that would have taken so much less energy. Would the following be a correct and reasonable answer: "The reorganization and formation of water took much less energy and resulted in heat being released." ?
 
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The solvated proton from the acid and the solvated hydroxide from the base are less stable (and have the potential to react...) than the water which results from their combining. The water is more stable than the separate ions. Energy is released into the environment upon this neutralization, and the increase in temperature can be observed (and measured).
 

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