Dilution is the process of adding another solvent to a solution in order to decrease its concentration, hence, maintaining the amount of solute to a certain amount while increasing the total volume of the solution.
Another way of achieving dilution is by mixing a solution with a higher concentration of solute to that of a solution with lesser solute amount.
The process of dilution is very important in laboratory settings as the stock solutions or reagents are usually purchased in highly concentrated forms. Most of the laboratory experiments cannot be done with highly concentrated reagents, so the act of dilution must be done in order to taper the concentration into a lesser known one.
In the pharmacy setting, operators are taught certain dilution calculations with the basic formula represented as:
M1 V1 = M2 V2
- M1: refers to the original ‘known’ concentration of the solution;
- V1: refers to the original ‘known’ volume of the solution;
- M2: represents the concentration of the diluted solution; and
- V2: represents the final, usually ‘unknown’, volume of the solution.
Concentration of Solutions
Solutions are made up of two main components:
- Solute: refers to the dissolved material in the solution.
- Solvent: the liquid component where the solute is dissolved.
The concentration of the preparation depends on the amount of solute in a given amount of solvent, and in the laboratory setting, the two most common ways to depict concentration is molarity (M) and molality (m).
- Molarity refers to the molar concentration of a solute per liter of a solution.
- M = moles (n) of solute / L of solution
- Molality represents the ratio of the moles of a solute to the amount (kg) of a solvent.
- M = moles (n) of solute / kg of solvent
- Mole (n) is defined as 6.02214076 x 1023 of a chemical unit (atoms/molecules/ions, etc.). It must be well noted that the amount of atoms, etc., in a mole is the same for all substances. The concept of moles can also be used to determine the simplest formula of a compound and even to calculate the quantities involved in chemical reactions.
- n = grams of solute / molecular weight (g/n) of the solution
- Britannica. (2020). Mole. In Britannica.com encyclopaedia. Retrieved from: https://www.britannica.com/science/mole-chemistry
- Gleichmann, N. (2020). Molarity vs Molality: Formula and Definitions. Technology Networks. Retrieved from: https://www.technologynetworks.com/analysis/articles/molarity-vs-molality-formula-and-definitions-334119#:~:text=Both%20molarity%20and%20molality%20are%20measures%20of%20a%20chemical%20solution's%20concentration.&text=The%20molality%20describes%20the%20moles,the%20volume%20of%20a%20solution.
- Molarity. (n.d.). Khan Academy. Retrieved from: https://www.khanacademy.org/science/ap-chemistry/states-of-matter-and-intermolecular-forces-ap/mixtures-and-solutions-ap/a/molarity
- Solution Stoichiometry. (n.d.). Lumen Learning. Retrieved from: https://courses.lumenlearning.com/introchem/chapter/solution-stoichiometry/