What is the importance of dissolving a solute in a smaller volume of solvent?

Answer 1

Water is critical to all life as the universal solvent and that is due to its molecular shape, polarity and that it is the most common liquid on Earth. Other polar or charged molecules can dissolve into the fluid water making them available for biological reactions. Water then is a carrier for polar or charged molecules to move by diffusion or to move by current flow.

Most nonpolar molecules like lipids as hydrophobic molecules are excluded from dissolving, making it possible to partition cellular life using lipid membranes. Membrane compartments are essential for life to organize itself within, as the semipermeable boundary permits regulation of the contents and internal homeostasis of the aqueous solution. This is the cell theory of life based on the hydrophilic polar molecules and the hydrophobic nonpolar molecules shunning each other to form semipermeable compartments that allow osmotic movements between regions of high and low water potential.

Soluble minerals, carbohydrates, proteins, and nucleic acids make it possible to have complex sequential metabolic pathways. The membranes make it possible to isolate reactions and make then efficient.

Solubility makes it possible to dissolve dry powders (that are solids) or gasses into water so we can create mixtures for specific uses. Solubility makes it possible to make a cup of tea from dried leaves. It also makes it possible to sweeten it by dissolving sugar in it.

The dissolving process involves a consideration of the relative strength of three intermolecular attractive attributes.

1) solute-to-solute intermolecular cohesive attraction

2) solvent-to-solvent cohesive attraction

3) solute-to-solvent adhesion

The solute-solvent attractive forces must be as attractive as these first two intermolecular attractions. A solute is a non-covalently bonded molecular compound that is attracted to the fluid solvent more that the molecular components of the solute cohere to each other.

In detail about NaCl - when the attraction of the sodium cation for the oxygen dipole of the water molecule and the attraction of the chlorine anion for the hydrogen dipole is equal or greater than the attraction between the sodium to the chlorine, then the ionic bonds binding the sodium-to-chlorine and the cohesive hydrogen bonds holding water-to-water are overcome. The solute dissolves and disperses. Solvent molecules surround each ion forming a solvation shell.