Is CaCO3 Soluble Or Insoluble In Water, Acid, And Ethanol?

Is CaCO3 soluble or insoluble?

Ionic compounds are usually soluble in polar solvents like water. The positive cation gets attracted to the negative end of water (OH^–) and the negative side gets attracted to the positive side (H⁺). This makes dissolution possible. However, this does not seem to happen for all ionic compounds.

The focus of this article is CaCO₃, calcium carbonate, or calcite. CaCO₃ is one of the most abundant minerals on the earth’s crust. It is non-toxic and colorless.

It occurs as marble, limestone, and chalk, and it is a component of materials like eggshells, corals, seashells, oyster shells, and snail shells. These are by the way. Read on to find out whether CaCO₃ is soluble or insoluble and the reasons behind its solubility or insolubility.

Is CaCO₃ soluble or insoluble in water?

CaCO₃ is slightly soluble in water. It has a solubility of 0.013 g/L of water at 25 °C. This is due to the strong attraction between the calcium cations (Ca²⁺) and the carbonate anions (CO₃^2-).

In water, these ions are large and make the solution slow. It makes dissolution difficult and almost impossible. Among all carbonates – for alkali and alkali Earth metals – CaCO₃ has the lowest solubility.

Furthermore, CaCO₃ is a strong ionic compound. Within this solid is a strong electrostatic force of attraction that keeps the atoms tightly held together. The bonds are so strong and beyond being broken by polar solvents like water.

Two forms of energy determine the dissolution of solids in solvents. They are lattice energy and hydration energy. Hydration energy is the energy released when one mole of a substance dissolves in water. On the other hand, lattice energy is the energy that holds a crystal lattice together.

If hydration energy is higher than lattice energy, the substance becomes soluble. Conversely, a higher lattice energy means the substance is insoluble. CaCO3 has higher lattice energy, which makes it difficult to break them apart.

CaCO_{3 (S)} + H₂O _(l) ———> Ca(OH)_{2 (s)} + CO_{2 (g)}

However, the solubility of CaCO₃ in water will increase if there is an increase in temperature and the concentration of CO₂ in the water. Also, its solubility increases in rainwater due to an increase in the formation of the more soluble calcium bicarbonate.

Is CaCO₃ soluble or insoluble in acid?

CaCO₃ shows a higher solubility in acid than in water. It dissolves in acids to form a calcium salt, carbon dioxide, and water.

For instance, CaCO₃ reacts with hydrochloric acid, HCl, to produce calcium chloride salt, CaCl₂, and carbon dioxide. The reaction is as follows:

CaCO_{3 (s)} + 2HCl _(aq) ———> CaCl_{2 (aq)} + CO_{2 (g)} + H₂O _(l)

It produces calcium sulfate salt with sulfuric acid.

CaCO_{3 (s)} + H₂SO_{4 (aq)} ———> CaSO_{4 (s)} + CO_{2 (g)} + H₂O _(l)

Calcium carbonate is also soluble in nitric acid, producing calcium nitrate, carbon dioxide, and water.

CaCO_{3 (s)} + HNO_{3 (aq)} ———> Ca(NO₃)_{2 (aq)} + CO_{2 (g)} + H₂O _(l)

The reaction for phosphoric acid produces calcium phosphate salt.

3CaCO_{3 (s)} + H₃PO_{4 (aq)} ———> Ca₃(PO₄)_{2 (aq)} + 3CO_{2 (g)} + 3H₂O _(l)

Also, with ethanoic acid, it forms calcium ethanoate, carbon dioxide, and water.

CaCO_{3 (s)} + 2CH₃COOH _(aq) ———> Ca(CH₃COO)_{2 (aq)} + CO_{2 (g)} + H₂O _(l)

Is CaCO₃ soluble or insoluble in ethanol?

CaCO₃ is not soluble in ethanol. Ethanol is a less polar solvent than water. Its insolubility would be higher.

Factors that affect solubility

Temperature

The overall temperature of the reaction determines the solubility of the solute. The effect of temperature on solubility depends on whether the reaction is endothermic or exothermic.

Increasing temperature will increase solubility for an endothermic reaction and decrease the same for an exothermic reaction. Increasing temperature increases the vibration or kinetic energy of the solute molecules and weakens the intermolecular attractions that hold them together.

As a result, it is easier to break up the solute molecules and dissolve them in the solvent.

Pressure

The effect of pressure on solubility is negligible in solids and liquids. When temperature is constant, the solubility of gases depends on their partial pressures.

Polarity of solute

This applies to covalent compounds because ionic compounds do not show polarity. Polar solutes dissolve in polar solvents and nonpolar solutes dissolve in nonpolar solvents.

The molecular size of the solute

The larger the size of the molecules of the solutes, the more difficult it is for the solvent molecules to surround the solute molecules.

Solvent molecules will wrap around smaller solute molecules more easily increasing solubility. However, this may change with an alteration in temperature and pressure.

FAQs

How can CaCO₃ be separated from a mixture of CaCO₃ and water?

CaCO₃ is an insoluble salt. It does not dissolve in water. Therefore, it can be separated by simple filtration.

If the CaCO₃ solid also contains NaCl, dissolve the mixture with water. NaCl will dissolve and CaCO₃ will form insoluble precipitates. Filter the solution and separate the CaCO₃ precipitate.

Is CaCO₃ an ionic compound or a covalent compound?

CaCO₃ is an ionic compound. It contains a cation, a calcium ion (Ca²⁺), and an anion, a carbonate ion (CO₃^2-).

The carbonate ion has covalent bonds as the carbon and oxygen atoms are held together by covalent bonds. It suffices to say that calcium carbonate has both ionic and covalent bonds.

Which carbonate has the highest solubility?

All carbonates of alkali metals are highly soluble in water with potassium carbonate, K₂CO₃, topping the list. It fully dissolves in water and dissociates into its constituent ions.

Conclusion

Calcium carbonate, CaCO₃, is insoluble in water. The strong electrostatic forces of attraction make it difficult to dissolve into its constituent ions. However, you can get better results by raising the temperature or dissolving it in rainwater.

The solubility of CaCO₃ finds much relevance in water treatment. It dissolves in acid rain and helps to neutralize the water.

It is also used in the removal of detergents and cleansing agents from drinking water, and neutralization of toxic chemicals like calcium hydroxide and calcium polysulphide.

Expand your learning with this guide on the charge, reactions, and applications of the calcium ion.

Thanks for reading.