In percentage composition, what units are used?

Percentage composition is expressed as a mass ratio, specifically the mass of each component of the mixture compared to the total mass of the mixture. This can be represented as a percentage, which is calculated by taking the mass of a particular substance and dividing it by the total mass of the mixture, then multiplying by 100.

For example, if you have a solution consisting of different elements or compounds, to find the percentage composition of one component, you will measure its mass, determine the total mass of all components in the solution, and use the formula:

[ \text{Percentage Composition} = \left( \frac{\text{Mass of Component}}{\text{Total Mass}} \right) \times 100 ]

This makes mass per total mass the most appropriate unit for describing percentage composition in a chemical context. Other options, such as grams per liter, moles per liter, or grams per mole, pertain to concentration or molar mass rather than to the concept of how individual components contribute to the overall composition in percentage terms.