Final answer:
The molar mass of a compound is found by summing the atomic masses of its constituent atoms, and the percentage composition shows the mass percent of each element within the compound. This molar mass is used to calculate the percent by mass of each element by dividing the mass of the element in one mole of the compound, by the total molar mass, and multiplying by 100%.
Step-by-step explanation:
The molar mass of a compound is a crucial concept in chemistry, as it helps in determining the mass of one mole of that compound. The molar mass is calculated by summing the atomic masses of all the atoms present in the molecular formula of the compound. For instance, in carbon dioxide (CO₂), the molar mass is the sum of the mass of one carbon atom (about 12 g/mol) and two oxygen atoms (about 16 g/mol each), resulting in 44 g/mol for CO₂.
Additionally, the percentage composition of a compound, which shows the mass percent of each constituent element, is always consistent for a pure substance. It is computed by taking the mass of each element in one mole of the compound, dividing it by the molar mass of the compound, and then multiplying by 100%. An example would be calculating the percentage composition of a compound known to be composed of 13 carbon atoms, 18 hydrogen atoms, and 2 oxygen atoms. The process would involve using the atomic masses of these elements to determine the compound's molar mass and then using this value to calculate the percentage composition of each element.