Chemical Solution Concentration Formulas and Calculations

Understanding Chemical Solutions

To study chemical solutions effectively, you need to understand all types of mixtures and concentrations. While most concentrations can be calculated using the rule of three, it is common practice to use specific formulas. Below are the most important ones:

Common Concentration

The unit used for common concentration is g/L.

Molarity

The unit used for molarity is mol/L.

Hint: By replacing the number of moles (n) in the formula , we derive the following formula:

Mass Fraction (Title)

This concentration is a ratio, which means it is dimensionless.

or

Percentage

The concentration can also be expressed as a percentage (%).

Molar Fraction

Like the mass fraction, this concentration is a ratio and is therefore dimensionless.

Normality

The unit used for normality is N (Normal).

Gram-Equivalent

The unit used for the gram-equivalent is grams (g).

Dilution and Mixing of Solutions

For certain solutions, we must calculate the dilution. We can also mix solutions to obtain new concentrations. See the formulas for each specific case:

Dilution

Dilution occurs when a solvent (usually water) is added to a solution. We use the following formula:

In this formula, Molarity (M) can be replaced by Common Concentration (C).

Tip: On the left side of the formula, place the data for the initial, more concentrated solution. On the right side, place the data for the final, more diluted solution after water has been added.

Mixing Solutions with the Same Solute

or

Mixing Solutions with Different Solutes

In cases involving an acid and a base, neutralization reactions occur. The acid and base react to form a new product. You must take into account the chemical reaction and the stoichiometric coefficients.

Relationship Between Concentrations

To facilitate calculations, there are formulas that link different types of concentrations together:

Tip: Be careful with the distinction between density and concentration. Although the formulas may look similar, they are not the same. Density refers to the mass of the entire solution divided by the volume of the solution. Common concentration refers specifically to the mass of the solute divided by the volume of the solution.

Summary Table of Solution Formulas