Why is CO2 (Carbon dioxide) Soluble in Water?

Yes, CO₂ (Carbon dioxide) is soluble in water. ¹ It is soluble in water because CO₂ molecules can react with water molecules to form carbonic acid (H₂CO₃), which then dissociates into bicarbonate ions [(HCO₃)-] and hydrogen ions (H+), allowing for its dissolution in water.

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Explanation: Why is CO2 soluble in water?

Carbon dioxide (CO₂) is soluble in water due to its molecular properties and the nature of intermolecular forces involved.

When CO₂ dissolves in water, it undergoes a reaction called hydration, resulting in the formation of carbonic acid (H₂CO₃): ³

CO₂ + H₂O → H₂CO₃

The solubility of CO₂ in water can be attributed to several factors:

• Hydrogen bonding: Water molecules can form hydrogen bonds with each other due to the presence of hydrogen atoms with a partial positive charge and oxygen atoms with a partial negative charge. ⁴ When CO₂ dissolves in water, it can disrupt some of these hydrogen bonds, allowing water molecules to interact with CO₂ molecules through weaker intermolecular forces.
• Dipole-dipole interactions: The polar nature of water and polar bonds of carbon dioxide allows for dipole-dipole interactions between the positively charged hydrogen atoms of water and the negatively charged oxygen atom of CO₂. These interactions contribute to the solubility of CO₂ in water.

It is important to note that while CO₂ is soluble in water, its solubility is relatively low compared to some other gases. Factors such as temperature, pressure, and the presence of other solutes can influence the solubility of CO₂ in water. ⁵

What factors affect the solubility of CO2 in water?

The solubility of carbon dioxide (CO₂) in water can be influenced by several factors:

1. Temperature: Generally, the solubility of gases in water decreases as temperature increases. ⁶ This means that at higher temperatures, less CO₂ can dissolve in water. Conversely, at lower temperatures, the solubility of CO₂ increases. This relationship follows Henry’s Law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.
2. Pressure: Increasing the pressure of CO₂ above the water can enhance its solubility. ⁷ According to Henry’s Law, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas. Therefore, higher pressures of CO₂ will lead to greater solubility in water. This is the principle behind carbonation in carbonated beverages, where high-pressure CO₂ is dissolved in the liquid.
3. pH: The pH of water can influence the solubility of CO₂ because CO₂ reacts with water to form carbonic acid (H₂CO₃). Carbonic acid can dissociate into hydrogen ions (H+) and bicarbonate ions (HCO₃)-. In more acidic conditions (lower pH), the equilibrium shifts towards the formation of more CO₂ molecules. Therefore, lower pH values can increase the solubility of CO₂ in water.
4. Presence of other solutes: The presence of other solutes in water can influence the solubility of CO₂. ⁸ For example, the presence of dissolved organic compounds or other gases can compete for interactions with water molecules, potentially affecting the solubility of CO₂.

It is important to note that these factors can interact with each other, and the solubility of CO₂ in water is a complex equilibrium process that depends on multiple variables.

Further reading

Why is NH3 (Ammonia) Soluble in Water?
Why is Methanol (CH3OH) Soluble in Water?
Why is Acetone Soluble in Water?
Is Hexane Soluble in Water?
Why is Ethanol Soluble in Water?

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