What happens when an ionic compound dissolves in water?

Written by stuart withers Google
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What happens when an ionic compound dissolves in water?
The process of hydration prevents ionic bonds from reforming. (Photodisc/Photodisc/Getty Images)

Water is quite an amazing molecule. It’s essential for life and without it, well, we wouldn’t even exist. Water is great because it is a fantastic solvent. Solvents are substances that provide the perfect environment for dissolving various solutes, such as ionic compounds. Ionic compounds and other solutes dissolve in solvents because of electrical reactions between the atoms of both solutes and solvents.

Water molecules

Water is a type of polar molecule, which means it is a molecule that has a separation of electric charge. Water molecules carry a slight positive charge on one side and a slight negative charge on the other side (this is simply known in science as a dipole). The polarity of water is caused by arrangement of the atomic bonds within each water molecule. The way the negatively charged oxygen atoms and positively charged hydrogen atoms bond in water separate the positive and negative electric charges.

Ionic compounds

Ionic compounds, such as sodium chloride -- or “table salt” -- are made up of ions. Ions are molecules or elements which are either positively charged, known as “cations,” or negatively charged, known as “anions.” As opposite charges attract, ionic compounds are formed when ionic bonds happen between the negatively and positively charged ions. It is the composition of both negatively and positively charged ions in ionic compounds that causes them to dissolve in water.

Electrical interactions

As water molecules have a slightly positive and slightly negatively charged side, the positive cations and negative anions within ionic compounds are attracted to different sides of the water molecule. The positive cations are attracted to the negative side of the water molecules, and the negative anions are attracted to the positive side. The resulting electrical interactions between the ionic compound and the water cause the bonds within the ionic compound to weaken and eventually break. This in turn releases ions that have broken free from their bonds into the water.

Dissolving and hydration

Once the ionic bonds start breaking, the ions that are released into the water are quickly surrounded by water molecules, because water is a dipole and an electrical interaction between the water molecules and the separately charged ions takes place. This process is known as “hydration.” Hydration stops the ions in the ionic compound from reforming their bonds, and therefore the more the bonds break, the more the ionic compound dissolves. Eventually, all the ionic bonds will break and all of the ions will be hydrated by the water, causing the ionic compound to completely dissolve.

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