Percent Concentrations: Videos & Practice Problems

Mass percent is a crucial concept in chemistry that indicates the percentage of a specific solute in grams relative to the total mass of the solution, also measured in grams. To express solution concentrations, we can utilize various formulas, including mass/volume and volume percent. One important measure is mass/volume percent concentration, often abbreviated as m/v percent concentration.

The m/v percent concentration quantifies the amount of solute in grams dissolved in a specific volume of solution measured in milliliters. The formula for calculating mass/volume percent concentration is given by:

m/v \% = \left( \frac{\text{grams of solute}}{\text{milliliters of solution}} \right) \times 100\%

This formula allows for the straightforward calculation of the mass/volume percentage for any solution, providing essential information about the concentration of solutes in various applications.

Volume-volume percentage is a way to express the concentration of a solute in a solution. It indicates the volume of the solute in milliliters (mL) relative to the total volume of the solution, also measured in milliliters. The formula for calculating volume-volume percentage (v/v %) is given by:

$$ \text{v/v \%} = \left( \frac{\text{mL of solute}}{\text{mL of solution}} \right) \times 100\% $$

In this equation, the numerator represents the volume of the solute, while the denominator represents the total volume of the solution. By multiplying the fraction by 100%, you convert it into a percentage, providing a clear understanding of how much solute is present in the solution relative to the total volume. This concept is essential in various fields, including chemistry and pharmacology, where precise concentrations are crucial for reactions and formulations.

To determine the volume-volume percentage of ethanol in a 750 ml bottle of Listerine, we can use the formula for volume-volume percentage, which is expressed as:

Volume-Volume Percentage = \(\frac{\text{ml of solute}}{\text{ml of solution}} \times 100\%\

In this case, the solute is ethanol, which has a volume of 150 ml, and the total volume of the solution (the Listerine) is 750 ml. Plugging these values into the formula gives:

Volume-Volume Percentage = \(\frac{150 \, \text{ml}}{750 \, \text{ml}} \times 100\% = 20\%\

When considering significant figures, the volume of ethanol (150 ml) has 2 significant figures, while the total volume of the solution (750 ml) has 4 significant figures. Therefore, the final result should be expressed with 2 significant figures, resulting in a volume-volume percentage of 20.0%.