Molar Solution

Published: | Updated: September 16, 2020;

Definition - What does Molar Solution mean?

A molar solution is defined as an aqueous solution that contains 1 mole (gram-molecular weight) of a compound dissolved in 1 liter of a solution. In other words, the solution has a concentration of 1 mol/L or a molarity of 1 (1M). Physicists and chemists typically use this parameter to express concentrations of various substances.

Molar solutions and molarity measurements are frequently used in electrochemistry to quantify the concentration of ions in an electrolyte. The higher the concentration of a particular ion in a substance, the more aggressive it will likely be towards metals.

Molar solutions are also useful in predicting corrosion rates. For example, steel corrosion in a 1M hydrochloric acid solution can be assessed using weight loss and other electrochemical techniques. This information can then be used to perform calculations and evaluate steel corrosion in different situations.

Corrosionpedia explains Molar Solution

Substances are often mixtures of different compounds and elements. The Earth's atmosphere, for example, is a mixture of 78% nitrogen, 21% oxygen and 1% carbon dioxide and other gases. Even regular drinking water has traces of elements, such as zinc, magnesium and chlorine, among others. Therefore, being able to quantify solutions in terms of molar concentrations is essential.

For example, the gram molecular weight of sodium chloride (NaCl) is 58.44, i.e., 1 mole of the substance is 58.44g. If this amount of NaCl is dissolved in 1 liter (1L) of water, then the combined substance qualifies as a molar solution. Or, it can be said that we have a 1M NaCl solution.

Using this information, it is possible to scale the concentration as needed. For instance, 5.844g of NaCl can be dissolved in 1 liter of water to create a 0.1M solution. Alternatively, 5.844g of NaCl can be dissolved in 100mL of water to make a 1M sample, etc.

The Relationship Between Molar Solutions and Molar Concentration

While they may sound similar, a molar solution is not the same as molar concentration. Molar concentration, also known as molarity, is the number of moles per liter of solution (mol/L).

Molar concentration (Molarity) = mol of solute / L of solution

A molar solution, on the other hand, has 1 mol of solute contained in 1 liter of solution. In other words, a molar solution is simply a substance with a molarity of 1.

What Does It Really Mean To Have a Molar Solution?

To better understand what a molar solution truly represents, it is essential to know what a mole is. A mole is defined as 6.022 x 1023 molecules of any substance. This odd figure, known as Avogadro's constant, was chosen because the number of grams of 1 mole of a substance is roughly equal to its atomic weight. For example, 1 mole of water corresponds to its atomic weight, which is 18 grams.

Therefore, if a substance is a molar solution, that means that the solvent contains 6.022 x 1023 molecules of solute.

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