Molarity vs. Parts per Million: Comparing Solutions in Chemistry

This assignment compares Molarity and Parts per Million (ppm), two fundamental concepts in chemistry used to measure solution concentrations. Molarity, expressed as moles per liter, is used to determine the number of moles in a solution and is useful for comparing substances on a molecular basis. Parts per million, on the other hand, is the mass of a solute in a million parts of a solution, commonly used for measuring contaminants in water and soil. The assignment highlights that while molarity is beneficial for comparing substances based on their molecular concentrations, ppm is useful when dealing with substances without a defined molecular weight. It emphasizes the importance of molarity for bioassays and the application of ppm in measuring plant hormones, offering a clear distinction between the two measurement methods and their appropriate uses. References are provided to support the concepts discussed.

Running head: AP CHEMISTRY 1
Ap Chemistry
Student’s Name
Name of Institution

AP CHEMISTRY 2
Molarity vs Parts per Million
The two methods; molarity and parts per million are used to measure the concentration of
a solution. Molarity refers to the number of solute moles in every liter of solution. It is calculated
as follows;
Molarity= moles of solute
liters of solution
Parts per million is defined as the solute mass in a million sample of the amount of solution. It is
derived as shown below;
parts per million= mass of solute
liters of solution∗1000000
Molarity is the main unit of determining solution concentration. It is used to calculate the number
of moles in every liter of the solution. Molarity helps obtain the solvent volume or quantity of
solute. Parts per million is mostly applied in determining the concentration of contaminants in
water, soil, and sediments (Savva, 2019).
Both molarity and parts per million rely on the weight of a molecule of a substance, that
is, g/mol. The two measures of concentration differ in the sense that molarity determines the
number of moles per liter while parts per million calculate the mass per liter (Harris, 2011).
Molarity is the most beneficial to use since it helps in comparing different substances on a
molecular basis. For instance, comparing for potency in a bioassay. For as long as the substance
being measured can be classified in molecular form, it becomes more easy and common to use
molarity as the measure of the concentration. It is easy to compare solvents based on their
molecular concentration. The use of parts per million fails to allow comparison of substances
based on their molecules. Otherwise, ppm is much helpful whenever the substance under
measurement does not have an established and defined molecular weight, for example, extracts

AP CHEMISTRY 3
and mixtures (Katoch, 2011). It is preferable to use ppm in measuring concentration in plant
hormones because it makes it easier to compare the results with other given recipes.

AP CHEMISTRY 4
References
Harris, D. C. (2010). Quantitative chemical analysis. Macmillan.
Katoch, R. (2011). Expression of Concentration. In Analytical Techniques in Biochemistry and
Molecular Biology (pp. 9-28). Springer, New York, NY.
Savva, M. (2019). Units of Concentration and the Salt Factor. In Pharmaceutical
Calculations (pp. 61-92). Springer, Cham.