The concentration of a solution is determined by dividing the amount of solute by the total volume of the solution.

To elaborate, concentration measures how much of a specific substance, referred to as the solute, is mixed with another substance, known as the solvent. The solute is the substance that is dissolved, while the solvent is the medium that facilitates the dissolving process. Typically, the solvent is a liquid, such as water, but it can also be a gas or a solid.

Concentration is commonly expressed in moles per liter, abbreviated as mol/L or M (molar). A mole is a standard unit in chemistry that quantifies the amount of a substance. Specifically, one mole of any substance contains the same number of entities (which can be atoms, molecules, or ions) as there are in 12 grams of pure carbon-12.

To calculate the concentration of a solution, you need to know the amount of solute that has been dissolved and the total volume of the solution. The formula for calculating concentration is given by:

For instance, if you dissolve $0.5$ moles of sodium chloride in $1$ liter of water, the concentration of the solution would be $0.5$ mol/L or $0.5$ M.

It is crucial to remember that the volume of the solution refers to the total volume, not just the volume of the solvent. Therefore, when you add a solute to a solvent, the total volume of the solution will equal the volume of the solute plus the volume of the solvent.

Calculating the concentration of a solution is an essential skill in chemistry, as it helps you understand the properties of the solution and predict how it will behave in various circumstances.