# Can someone explain why this dissolution is exothermic rather than endothermic?

• IntegrateMe
In summary, two students performed an experiment where they dissolved 6.32 g of KOH in 100 g of water. The initial temperature of the water was 27.0°C and after the dissolution, it increased to 42.5°C. This shows that the dissolution was exothermic, meaning that energy was released into the surroundings, causing the water to become warmer. If the dissolution had been endothermic, the water would have become cooler as energy would have been taken from the surroundings.
IntegrateMe
A pair of students found the temperature of 100 g of water to be 27.0°C. They then dissolved 6.32 g of KOH in the water. When the salt had dissolved, the temperature of the water was 42.5°C.

If the temperature of the water is raised, doesn't that mean it retained heat, thus showing that the dissolution was endothermic? I'm having trouble understanding why it is exothermic. Can someone please explain?

Exothermic means that energy is released by the chemical reaction. In other words, energy is an output of the reaction, along with the reaction products. Endothermic means that energy is an *input* to the reaction. In other words, the reaction won't occur unless if you give energy to the reactants. So, if the dissolution of potassium hydroxide had been endothermic, then the KOH would have had to steal energy from the surroundings (the water, in this case) in order to dissolve. Therefore, heat would have been removed from the water and the water would have become cooler. Instead, since the dissolution is exothermic, energy is released into the surroundings. So heat is transferred from the dissolving KOH into the water, which gets warmer as a result.

## 1. What is dissolution and why is it important?

Dissolution is the process of a substance, called the solute, being dissolved in a solvent to form a solution. It is important because it allows for the mixing and dispersal of substances, which is crucial for many chemical and biological processes.

## 2. What is the difference between exothermic and endothermic reactions?

An exothermic reaction releases heat, causing the surroundings to become warmer. On the other hand, an endothermic reaction absorbs heat, causing the surroundings to become cooler.

## 3. How can you determine if a dissolution is exothermic or endothermic?

The enthalpy change (ΔH) of a reaction can be used to determine if a dissolution is exothermic or endothermic. If ΔH is negative, the reaction is exothermic, while a positive ΔH indicates an endothermic reaction.

## 4. Why is this specific dissolution exothermic rather than endothermic?

The specific dissolution in question is exothermic because the energy released during the formation of the solution is greater than the energy required to break the bonds between the solute particles. This results in a net release of energy, making the reaction exothermic.

## 5. Can the temperature of a dissolution affect whether it is exothermic or endothermic?

Yes, the temperature can affect the enthalpy change of a dissolution reaction. In some cases, a dissolution may be endothermic at low temperatures and become exothermic at higher temperatures, as the increased kinetic energy allows for more efficient bond-breaking and bond-making processes.

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