When ammonium chloride dissolves in water, the solution becomes colder. (a) Is the solution process exothermic or endothermic?

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First, let's understand the terms exothermic and endothermic. An exothermic process is one that releases heat into its surroundings, causing the temperature of the surroundings to increase. An endothermic process, on the other hand, absorbs heat from its surroundings, causing the temperature of the surroundings to decrease.

In this case, when ammonium chloride dissolves in water, the solution becomes colder. This indicates that heat is being absorbed from the surroundings (the solution) into the system (the dissolving ammonium chloride).

Therefore, the process of ammonium chloride dissolving in water is an endothermic process.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Endothermic and Exothermic Processes

Endothermic processes absorb heat from the surroundings, resulting in a decrease in temperature, while exothermic processes release heat, causing an increase in temperature. In the context of dissolving substances, if the solution becomes colder, it indicates that heat is being absorbed from the surroundings, suggesting an endothermic reaction.

Dissolution of Ionic Compounds

When ionic compounds like ammonium chloride dissolve in water, they dissociate into their constituent ions. This process requires energy to overcome the ionic bonds in the solid and to separate the ions, which can lead to a cooling effect if the energy required exceeds the energy released during hydration of the ions.

Thermodynamics of Solution Formation

The thermodynamics of solution formation involves the balance between the energy required to break solute-solute and solvent-solvent interactions and the energy released from solute-solvent interactions. If the energy absorbed during the dissolution process is greater than the energy released, the overall process is endothermic, leading to a decrease in temperature of the solution.

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An ionic compound has a very negative ∆H_soln in water (b) Which term would you expect to be the largest negative number: ∆H_solvent, ∆H_solute, or ∆H_mix?

Textbook Question

When ammonium chloride dissolves in water, the solution becomes colder. (b) Why does the solution form?

Textbook Question

The first stage of treatment at the reverse osmosis plant in Carlsbad, California, is to flow the water through rock, sand, and gravel as shown here. Would this step remove particulate matter? Would this step remove dissolved salts?

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