Question

Water and glycerol, \(\mathrm{CH}_{2}(\mathrm{OH}) \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{2} \mathrm{OH}\), are mis- cible in all proportions. What does this mean? How do the OH groups of the alcohol molecule contribute to this miscibility?

Short answer

Water and glycerol are miscible in all proportions due to the polar nature of both molecules. The presence of OH groups in glycerol allows it to form hydrogen bonds with water molecules, resulting in a homogeneous solution. The miscibility of these substances is attributed to the ability of their OH groups to participate in hydrogen bonding, overcoming individual intermolecular forces.

Step-by-step solution

Understand miscibility

Miscibility refers to the ability of two or more substances to mix together in all proportions to form a homogeneous solution. In this case, water and glycerol are miscible, which means that any amount of water can be mixed with any amount of glycerol to create a uniform solution.

Examine the glycerol molecule

Glycerol, also known as glycerine, is an organic compound with the molecular formula \(\mathrm{CH}_{2}(\mathrm{OH}) \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_{2} \mathrm{OH}\). It has a central carbon atom connected to two other carbon atoms, each of which is bonded to a hydroxyl group (OH). The OH group is a polar functional group, which means it has a partially positive hydrogen atom and a partially negative oxygen atom.

Analyze water's properties

Water is a highly polar molecule due to the presence of two hydrogen atoms bonded to one oxygen atom. The difference in electronegativity between hydrogen and oxygen leads to a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows water to form hydrogen bonds with other polar molecules.

Understand the role of OH groups in miscibility

The presence of OH groups in the glycerol molecule makes it a polar substance. The OH groups can form hydrogen bonds with the water molecules, and these intermolecular forces between the glycerol and water molecules overcome the intermolecular forces within the individual substances. As a result, glycerol dissolves in water, leading to miscibility in all proportions.

Recap the solution

To summarize, water and glycerol are miscible in all proportions because their polar structures allow them to form hydrogen bonds with each other. The OH groups present in the glycerol molecule are responsible for this miscibility, as they enable glycerol to form hydrogen bonds with water molecules, leading to a homogeneous solution.