Is Calcium Carbonate Soluble In Water?

No, calcium carbonate is insoluble in water.

Calcium carbonate is known as calcite, which is an inorganic and ionic compound.

Most ionic compounds become ionized when they are dissolved in water.

However, calcium carbonate is an exception. It doesn’t dissolve in water.

This is true for most metal carbonates.

Let’s discuss calcium carbonate and its solubility in detail.

Is Calcium Carbonate Soluble In Water? (Explained)

What is Calcium Carbonate?

Calcium carbonate, or calcite, is an inorganic chemical compound with the chemical formula CaCO₃.

It is found in Earth’s crust and comes in several different forms, like limestone, marble, etc.

It occurs naturally as a white mineral in limestone, chalk, and marble.

Corals, shells of oysters, eggs, seashells, and snail shells are also made up of calcium carbonate.

Calcium carbonate is an ionically strong compound.

There is a strong electrostatic force and the atoms are very tightly bound together because of it.

These bonds are so strong that they are hard to break.

This is what happens when you dissolve calcium carbonate in water.

The strength of bonds makes calcium carbonate insoluble in water, since they do not break.

Additionally, calcium carbonate does not ionize in water.

Therefore, calcium carbonate is not soluble in water.

Things to remember:

Lattice energy and hydration energy are two factors that determine ionic compound dissolution.

Calcium carbonate has very high lattice energy, which also explains why it does not dissolve in water.

Water and carbon dioxide are produced from the acid reaction with the carbonate, and calcium acetate resulting from this reaction is water-soluble.

What does Solubility of a Substance Mean?

The solubility of a chemical substance refers to the ability of the solute (usually a solid, liquid, or gas) to dissolve in a solvent (usually a liquid) to form an aqueous solution.

Solvents, temperature, and pressure all affect a substance’s solubility.

By measuring the concentration of the saturated solution, you can determine the solubility of a substance in a specific solvent.

When the concentration of a solution is no longer increased by adding more solute, it is considered saturated.

Factors Affecting Solubility of a Substance

Substances have different physical and chemical properties, which determine their solubility.

Furthermore, it can also be manipulated under certain conditions.

These include the temperature, the pressure, and the type of bond and forces between the particles.

1. Temperature:

Increasing the temperature will increase the solubility of a solute.

A solute is dissolved by water at either 20°C or 100°C.

Solids or liquids that are sparingly soluble can be fully dissolved by increasing their temperature.

When it comes to gaseous substances, however, the temperature actually affects solubility the other way.

As the temperature rises, the gas expands and escapes the solvent.

2. Types of Bonds and Forces:

Similar things dissolve into similar things.

Every molecule possesses a different type of intermolecular force and bond.

Like substances are more likely to be soluble than, unlike substances.

In water, for example, ethanol is soluble easily, since it is a polar solvent.

3. Pressure:

Solids and liquids are much less affected by pressure than gaseous substances.

Gases have a greater chance of being soluble when their partial pressure increases.

A soda bottle is a good example of how CO₂ is bottled under pressure.

Why is Calcium Carbonate Insoluble in Water?

In simple terms, a substance’s solubility relates to how easily it dissolves in another substance – a solvent – and forms a solution.

An ionic compound is soluble in water and can form ions when broken down.

As we know that calcium carbonate is an ionic compound, it should practically show the same behavior.

However, calcium carbonate, like most metal carbonates, is insoluble in water.

Water is a polar solvent.

The original structure of an ionic compound is broken down when water dissolves it, resulting in separate ions.

An ionic compound’s solubility in water is therefore determined by its lattice energy and hydration energy.

Hydration energy is the energy released upon dissolving one mol of a substance in water, and it is dependent upon the ion charge density.

As for crystal lattice energy, it is a measure of how a compound holds its crystalline structure together.

It is based on the distance between two atoms in a molecule.

A compound becomes soluble in water if its hydration energy exceeds its lattice energy, but remains insoluble if the lattice energy exceeds the hydration energy.

As a result, the difference between a compound’s lattice energy and its hydration energy determines its solubility in water.

The lattice energy of calcium carbonate is 2860 KJ/mol.

The hydration energy of Ca²⁺ ions is -189 KJ/mol, whereas that of CO₃^2-ions is – 40 KJ/mol.

Water does not dissolve the CaCO₃ molecules because of the high value of lattice energy compared with hydration energy.

The solubility of calcium carbonate is very low in pure water, about 0.013 g/L when the temperature is 25 °C.

However, the solubility trend of carbonate deviates from the normal trend; calcium carbonate is more soluble in cold water as the temperature decreases, and this is the opposite of the normal trend.

Is Solubility Important to Identify a Substance?

Yes, solubility is important in identifying a substance.

Solubility measures can be used to determine the size, polarity, and presence of fundamental or acidic functional groups of an unknown compound.

A compound must undergo an ionization and, therefore, a chemical reaction to become soluble in aqueous acid or base.

Final Thoughts

The lattice energy of calcium carbonate is higher compared to its hydration energy, so it is insoluble in water.

Additionally, the calcium carbonate has a low solubility product of 3.3 X 10-9, which indicates that it cannot dissolve in water.

Calcium carbonate cannot dissolve in pure water, but it dissolves in rainwater due to the presence of atmospheric carbon dioxide.

The calcium carbonate in rainwater is soluble due to the presence of atmospheric carbon dioxide that lowers the pH of the water and makes it somewhat acidic.