An example of percent by mass is ordinary bleach, which is 5.25% NaOCl (sodium hypochlorite) by mass; this means that every 100 grams of bleach contains 5.25 grams of NaOCl.
Percent by mass, also known as mass percentage, expresses the concentration of a substance in a mixture or solution. It is calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100%. This provides a straightforward way to understand the proportion of a specific component within a larger mixture.
Formula:
Percent by Mass = (Mass of Solute / Mass of Solution) * 100%
Examples:
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Bleach: As mentioned earlier, household bleach typically contains around 5.25% sodium hypochlorite (NaOCl) by mass. This signifies that in 100 grams of bleach solution, there are 5.25 grams of NaOCl. The remainder is primarily water.
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Sodium Hydroxide Solution: If 6 grams of sodium hydroxide (NaOH) are dissolved in 50 grams of water, the mass percentage of NaOH can be calculated as follows:
Percent by Mass = (6 g / (6 g + 50 g)) 100% = (6 g / 56 g) 100% ≈ 10.71%
This indicates that the solution is approximately 10.71% NaOH by mass.
Importance:
Understanding percent by mass is crucial in various fields:
- Chemistry: For preparing solutions with specific concentrations.
- Manufacturing: Ensuring product quality and consistency.
- Environmental Science: Assessing pollutant levels in water or air samples.
- Food Industry: Controlling ingredient proportions for taste and preservation.
