Calcium carbonate, or CaCO3, is a chemical substance with the formula CaCO3. It is a calcium carbonic salt that is also known as calcite or aragonite, the mineral ores of which it is made.
It’s common in rocks and also makes up the majority of seashells, eggshells, snail shells, pearls, and corals. It’s a non-toxic, odourless white substance. It is alkaline and reacts with acids to produce carbon dioxide.
We’ll look at whether CaCO3 is soluble in water in this post.
So, is CaCO3 water soluble? CaCO3 is insoluble in water because the calcium carbonate molecules have extremely high electrostatic forces of attraction. Even though calcium carbonate is an ionic material, the forces are so strong that breaking the connection between the calcium and carbonate ions is impossible, thus CaCO3 will not dissociate in water. CaCO3 has a very low solubility product of 3.3 * 10-9, indicating that it is not soluble in water.
The majority of metal carbonates are water insoluble.
In the next sub-topics, we’ll look at the reasons for CaCO3’s insolubility in water. Continue reading!
Why is CaCO3 not water soluble?
The ability of a substance, or solute, to form a solution when dissolved in another substance, or solvent, is called solubility.
Most ionic chemicals dissolve in water and break down into ions. Because calcium carbonate is an ionic chemical, it should behave similarly, however unlike most other metal carbonates, CaCO3 molecules do not dissolve in water.
Water is a polar solvent, and when any ionic compound is dissolved in it, its original structure is destroyed, resulting in the formation of distinct ions.
As a result, an ionic compound’s solubility in water is determined by its hydration energy and lattice energy.
The energy generated when one mole of a material is dissolved in water depends on the charge density of ions, whereas lattice energy is the energy responsible for binding the crystal lattice together in a compound and is mostly determined by the distance between the two atoms of a molecule.
When a compound’s hydration energy exceeds its lattice energy, the substance becomes water soluble, however when the lattice energy exceeds the hydration energy, the substance remains insoluble.
As a result, a compound’s solubility in water is determined by the difference between its lattice and hydration energies.
The lattice energy of calcium carbonate is 2860 KJ/mol, while the hydration energy of Ca2+ is -189 KJ/mol and the hydration energy of CO32- ion is – 40 KJ/mol.
CaCO3 molecules do not dissolve in water because their lattice energy is much higher than their hydration energy.
In addition, the solubility chart below shows the solubility of several compounds made up of different anions and cations:
Here,
• The letter S stands for soluble.
• I’m an abbreviation for “insoluble.”
• sS is an abbreviation for “slightly soluble.”
• The letter X stands for “others.”
When looking at the combination of calcium and carbonate ions, it is evident that the two ions are insoluble in water.
Carbonates are normally not soluble in water, with the exception of sodium, potassium, and ammonium, which are alkali metal carbonates, while magnesium carbonates are marginally soluble in water, according to solubility trends.
Calcium hydrogen carbonate, or Ca(HCO3), on the other hand, is water soluble.
Is Calcium Carbonate Soluble in Cold Water?
The typical trend of a compound’s solubility is that it increases with temperature.
This is owing to the additional energy provided by the kinetic energy of molecules, which aids in overcoming the lattice energy and breaking the interatomic bonds in the molecule.
Calcium carbonate has an extremely low solubility in pure water, about 0.013 g/L at 25 °C.
However, the solubility trend for carbonate is the inverse of the typical tendency, meaning that the solubility of calcium carbonate in water increases as the temperature falls, making it soluble in cold water.
Carbonate ions become more mobile as the temperature drops, and when the temperature rises, the carbonate ions precipitate out of the solution.
CaCO3 solubility in water is also influenced by the pressure and pH of the solution.
As the pressure rises, so does the solubility.
Calcium carbonate molecules are also easily soluble in rainwater because of this. The generation of carbonic acid is caused by the presence of dissolved carbon dioxide.
Is it true that CaCO3 reacts with water?
Calcium carbonate does not react with water under normal conditions.
When CaCO3 is added to water, the majority of calcium carbonate molecules precipitate on the bottom, with only a small proportion of molecules dissolved.
CaCO3 molecules, on the other hand, combine with rainfall to generate soluble calcium bicarbonate or calcium hydrogen carbonate.
The reaction takes place because carbon dioxide from the atmosphere is dissolved in the rainwater.
As a result of the creation of carbonic acid, the pH of the water drops.
The following is an example of a reaction:
Ca(HCO3)2 = CaCO3 + CO2 + H2O
In the long run, this process is responsible for rock erosion and the creation of caverns.
This is also why some areas of the country have high levels of dissolved calcium in their water (hard water).
What Causes CaCO3 to Be More Soluble?
Because calcium carbonate is insoluble in water, we’ll investigate the parameters that influence CaCO3 molecule solubility in rainwater using the procedure described in the preceding section.
The following are the various factors to blame:
• Temperature: As previously stated, a rise in temperature reduces the solubility of calcium carbonate in water, whilst a reduction in temperature increases it.
You should also read the page on how temperature affects ph.
• Water: Because the process is reversible, increasing the concentration of water moves the equilibrium to the right, allowing more ions to dissolve.
• Carbon dioxide: An increase in the amount of dissolved CO2 causes the equilibrium to shift to the right, causing more ions to dissolve in the solution.
• pH: As previously stated, dissolved CO2 causes the pH of the solution to drop.
Because the solubility of calcium carbonate increases with a fall in pH and decreases with an increase in carbon dioxide, the solubility of calcium carbonate increases with a decrease in pH and vice versa.
• Salts: Varied salts have different effects on the solubility of CaCO3.
If the salts present are composed of common ions, such as calcium carbonate, the solubility will decrease, however if other salts are present that do not contain any common ions, the solubility will increase.
Which Carbonates are Water Soluble?
With a few exceptions, most metal carbonates do not dissolve in water, but most alkaline metal carbonates do.
Potassium carbonate (K2CO3), Sodium carbonate (Na2CO3), and all other group 2 carbonates, with the exception of lithium carbonate, are soluble in water.
The presence of a single electron in the valence shell of alkali metals causes them to have a charge value of +1 because stability needs just one electron to be given away.
The attraction between oppositely charged atoms holds the various ions of alkali metal salts (such as carbonates) together.
Because water has a strong dipole moment, alkali metal salts dissolve easily in it due to charge separation.
Due to the small size of the lithium ion, it is not possible to break the bond energetically at room temperature, hence the salts do not dissolve in water.
When added to water, all alkaline earth metal compounds, as well as the carbonates of p-block and d-block elements, are insoluble and create a white precipitate.
CaCO3’s properties
Calcium carbonate is found in the form of limestone, marble, and other minerals. It’s a calcium salt that’s alkaline.
The following table lists the many properties of calcium carbonate:
| Chemical Name | Calcium Carbonate |
| Chemical Formula | CaCO3 |
| Molar Mass | 100.0869 g/mol |
| Appearance | Fine white powder |
| Taste | Chalky |
| Odor | Odorless |
| Melting Point | 1339 °C |
| Boiling Point | Decomposes before it boils |
| Density | 2.711 g/cm3 for calcite2.83 g/cm3 for aragonite |
| Solubility | 0.013 g/L at 25 °C |
| Solubility product | 3.3 X 10-9 |
| pH | 9 |
CaCO3’s Applications
The following are some of the most common applications for calcium carbonate:
• Calcium carbonate is widely utilised as a building material since it is found in limestone, marble, and other similar materials. It is found in a number of historical monuments.
• Calcium carbonate is used in the sugar beet refining process after it has been calcined with anthracite.
• In the oil business, it’s employed as a bridging and filter cake-sealing agent.
• It’s also the key ingredient in a lot of acid-relieving antacids.
• It’s also utilised as a phosphate binder in the treatment of hyperphosphatemia and as a filler for numerous pills.
• Agricultural lime (calcium carbonate) is used to neutralise acidic soil.
Conclusion
Calcium carbonate is not soluble in water because the compound’s lattice energy is much higher than its hydration energy.
Furthermore, the CaCO3 compound’s solubility product is exceedingly low (3.3 X 10-9), indicating that it cannot dissolve in water.
Solubility generally increases as temperature rises, however in the case of CaCO3, it rises as temperature decreases.
Calcium carbonate does not dissolve in pure water, but it does dissolve in rainfall due to dissolved atmospheric carbon dioxide, which lowers the pH of the water, making it somewhat acidic.
Water does not dissolve most metal carbonates. With the exception of helium, alkali metal carbonates dissolve in water.
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