Solubility of Ethanol – Is Ethanol Soluble in Water and in Hexane?
The solubility of ethanol is one of the factors that differentiate it from other alcohols. Solubility refers to the chemical property of a substance that enables it to dissolve in a solvent. The solubility of a substance can be measured based on the maximum amount of the substance, which is called the solute, that can dissolve in a solvent at equilibrium. Once dissolved, the resulting solution is known as the saturated solution.
Ethanol Solubility in Water
The first question asked when the solubility of ethanol is concerned is, “Is ethanol soluble in water?” The answer is quite simple. In fact, ethanol is widely known as one of the substances that are completely soluble in water. It is often used as an example of a substance that has a high solubility in water.
Like other alcohols, ethanol has a non-polar carbon chain connected to a polar OH group or hydroxyl functional group. This group is capable of forming hydrogen bonds with the same hydroxyl functional group also found in the water. So when ethanol is mixed with water, the ethanol molecules are retained but are able to form new bonds with the water molecules.
Thus, due to its polar OH group, ethanol is miscible and soluble in water, just like methanol and propanol, which also have their respective OH groups. However, there are other alcohols such as pentanol, hexanol, and heptanol that are not as soluble in water.
What is unique about the solubility of ethanol is that ethanol is known to be infinitely soluble in water, as compared to other substances that are soluble in water but at a lower range.
Ethanol Solubility in Hexane
It is easy to understand why ethanol is soluble in water, but another common question asked regarding ethanol solubility is, “Is ethanol soluble in hexane?”
The fact is that ethanol is not soluble in hexane, nor is it miscible in hexane. Hexane is made up of eight hydrocarbon molecules, which is why it is known as a symmetrical hydrocarbon. Due to this, it is not capable of mixing with water. When hexane is added to water, it will simply float on top of the water.
But unlike water, ethanol consists of two carbon molecules similar to what hexane is made up of. However, unless the carbon molecules in ethanol can increase to more than eight, it cannot form carbon bonds with hexane. Hexane also does not have an OH group, so it will not be able to form hydrogen bonds with ethane. Due to these reasons, ethanol will not dissolve in hexane.
But while ethanol is not soluble in hexane, it is miscible with hexane, which is known as a light aliphatic hydrocarbon. Ethanol is generally known to be polar because its OH group is more dominant than its hydrocarbon chain. However, it does have a non-polar end. Thus, hexane, which is made up of non-polar molecules, allows a certain level of miscibility with ethanol’s non-polar end.
The unique solubility of ethanol is due mainly to its very versatile nature as it has both a polar and non-polar end. Hexane, which does not have a hydrogen group and is non-polar, is not soluble in or miscible with water, which is the most polar substance. But since ethanol has a non-polar hydrocarbon chain and a polar OH group, it is both soluble in and miscible with water and also miscible with hexane.