Heat of Reaction Experiment, High school level

In summary, the question is asking to explain how heat is liberated in a reaction where Na+ ions are separated from OH- ions, even though the overall process involves energy absorption. Previous discussions on this topic have not provided a clear answer. The proposed solution suggests that the reorganization and formation of water during the reaction results in heat being released. This is because the water is more stable than the separate ions, leading to an exothermic reaction.
  • #1
bethanyd
11
0
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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  • #2
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).
 
  • #3


Your answer is correct and reasonable. In this reaction, HCl and NaOH react to form water (H2O) and sodium chloride (NaCl). The process of dissociation, where the Na+ and OH- ions are separated, does require energy. However, the formation of water from the hydrogen and hydroxide ions releases a much larger amount of energy, resulting in an overall exothermic reaction. This excess energy is released in the form of heat. So, your explanation of reorganization and formation of water taking less energy and resulting in heat being released is accurate.
 

What is the purpose of a heat of reaction experiment?

The purpose of a heat of reaction experiment is to measure the amount of heat released or absorbed during a chemical reaction. This can help determine the energy changes that occur during the reaction and provide insight into the nature of the reaction.

What materials are needed for a heat of reaction experiment at a high school level?

The materials needed for a heat of reaction experiment at a high school level typically include a calorimeter, thermometer, reactants, and any necessary supporting equipment such as beakers, stirrers, and a heat source. Safety equipment, such as goggles and gloves, should also be used.

How is the heat of reaction calculated in this experiment?

The heat of reaction is calculated by measuring the temperature change in the reactants or products during the reaction. This change in temperature is then used in the equation Q = mCΔT, where Q is the heat released or absorbed, m is the mass of the substance, C is the specific heat capacity, and ΔT is the change in temperature.

What safety precautions should be taken during a heat of reaction experiment?

Some safety precautions to take during a heat of reaction experiment include wearing safety equipment, such as goggles and gloves, working in a well-ventilated area, and using caution when handling hot or hazardous materials. It is also important to follow the instructions carefully and have a teacher or adult present to supervise the experiment.

How can the results of a heat of reaction experiment be used?

The results of a heat of reaction experiment can be used to understand the energy changes that occur during a chemical reaction, as well as determine the efficiency of the reaction. This information can also be applied to real-world situations, such as in the development of new materials or processes that require specific energy changes.

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