Which equation represents the percentage by mass of an element in a compound?

The equation that represents the percentage by mass of an element in a compound is derived from the concept of mass ratios. To determine the percentage by mass of a specific element within a compound, you take the mass of that element and divide it by the total mass of the compound. This fraction is then multiplied by 100 to convert it into a percentage.

The rationale behind this equation is straightforward: the percentage signifies how much of the total mass is contributed by the specific element. By focusing on the mass of the element relative to the entire mass of the compound, this equation accurately captures the proportion of the element within the compound, making it essential for calculations in various applications of chemistry, such as stoichiometry or analyzing the composition of compounds.

In contrast, the other options do not appropriately reflect this relationship. For example, dividing the mass of the compound by the mass of the element does not yield a meaningful ratio regarding the composition. Similarly, other configurations presented in the choices do not align with the established method for calculating percentage by mass. Adopting this method ensures precise and accurate determination of how much of a compound's mass is attributable to a specific element.