How does carboxylic acid dissolve in water and its physical properties

Carboxylic acid dissolve in water to form a carbonic acid and a hydronium ion. As the reaction proceeds, the equilibrium shifts from the left side to the right side, until all of the reactants are consumed and no more reactant molecules remain. The hydrolysis products that result from this process include hydrogen gas (H₂) and a carboxylate salt such as sodium acetate or acetic acid. At equilibrium, the concentrations of all products are equal to the concentrations of the reactants. The key is to identify all reactant and product molecules and then balance them.

The reaction between a carboxylic acid, like acetic acid (CH₃COOH) and water can be described by this equation:

CH₃COOH + H₂O <-> H₃O+ + CH₃COONa

In this equation, carboxylic acid molecules (CH₃COOH) and water molecules (H₂O) combine to form hydronium ions (H₃O⁺) and carboxylate ions (CH₃COONa). The product, carboxylate ions, is a salt; it combines with water to form the corresponding carboxylic acid (CH₃COOH) in solution. This shows carboxylic acid dissolve in water.

Carboxylic acids can be either strong or weak. In solutions of high concentration, such as concentrated acetic acid, the reaction proceeds according to the expression:

CH₃COOH <-> CH₃COONa + H₂O

In this case, the equilibrium shifts toward the right side. At equilibrium, however, all three molecules are present in equal concentrations.

Carboxylic acids that are strong, like acetic acid, form only a weak carbonic acid (H₂CO₃) and a hydronium ion when reacted with water. In fact, the reaction of a strong acid such as sulfuric acid (H₂SO₄) with water is even more complex because it involves carbon dioxide in addition to water. This is because carbon dioxide can be viewed as both a gas and an acid. The more common explanation for this apparent paradox is that H₂SO₄ dissociates into its constituent parts: sulfur trioxide (SO₃) and hydrogen sulfide gas (H₂S). The reaction of sulfur trioxide with water (also known as dissociation) is as follows:

H₂SO₄ <-> H₂O + SO₃ + H₂S

Carbonic acid, H₂CO₃ is an intermediate in the formation of the molecules that will be discussed later. Carbonic acid, which forms in part by way of water molecules hydrogen bonding with carbon dioxide, has a very short lifetime. In fact, carbonic acid has a lifetime of about one nanosecond. This type of reaction, where something reacts to form other things and then itself reverts back to a less energetic state is called an equilibrium reaction.

Physical properties of carboxylic acid

1.Odor of carboxylic acid

The smell of acetic acid is sour and pungent, like that of vinegar. It is well known for its sharp, vinegar-like smell. The smell of acetic acid can be detected from the vapors of a dilute solution with a concentration as low as 0.012%.

2.Carboxylic acid boiling point and melting point

The boiling points of different carboxylic acids vary widely, ranging from 78℃ (m-COOH) to 202℃ (p-C₆H₅COOH). At normal pressure, the melting point is approximately 30-40℃; higher than the boiling point. The melting points are more than 100℃; lower at low pressure. The melting points of carboxylic acids decrease with increasing chain length, whereas their boiling points increase with increasing chain length.

3.Carboxylic acid density

The density of saturated solutions of some typical carboxylic acids in water at 25℃ is: The density differs widely depending on the substitution pattern on the ring and the degree of unsaturation. The densities are typically 1.05-1.20 g/cm³. There is no direct correlation between solubility in water and molecular weight; only a weak correlation exists between solubility and molecular volume (a long hydrocarbon chain lowers solubility).

4.Carboxylic acid polymorphism

In organic compounds, the term polymorphism describes the difference in physical properties that result from different isomers having the same molecular formula. There are many different types of isomers that can arise in simple organic molecules. For example, two hydrocarbons with the same empirical formula (CX) can have a variety of physical and chemical properties. The terms cis and trans are used to refer to one or more substituents on a carbon atom of a carboxylic acid around which all the aromatic and resonance configurations lie. This gives rise to two groups of structural isomers, called cis-forms and trans-forms, respectively.

In conclusions, carboxylic acid dissolve in water when a strong base treat with carboxylic acid. This reaction is very easy and safe to do at home or in the lab.