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Molar mass is a fundamental concept in chemistry that helps us convert between the mass of a substance and the amount of substance, expressed in moles. The molar mass is particularly useful for calculating the masses of reactants and products in chemical reactions. It is expressed in grams per mole (g/mol) and is the sum of the atomic masses of all the atoms in a molecule. In the exercise, we calculated the molar mass of galena (PbS), which is made of lead (Pb) and sulfur (S).

• The molar mass of Pb is 207.2 g/mol,
• The molar mass of S is 32.1 g/mol.

By adding these values, we found the molar mass of PbS to be 239.3 g/mol. Understanding molar mass is essential for stoichiometric calculations, ensuring we can accurately determine the proportions of substances involved in reactions.

Mass fraction is a way to express the concentration of a component in a mixture, denoted as a fraction of the total mass. It is especially useful in scenarios where you need to calculate how much of a specific element or compound is present in a given sample. In the step-by-step solution, we used mass fraction to determine how much lead (Pb) is present in galena (PbS). The mass fraction is calculated by dividing the molar mass of the component of interest by the molar mass of the entire compound. For example, in galena (PbS),

• the mass fraction of Pb is calculated as \( \frac{207.2}{239.3} \approx 0.866 \).

This means that 86.6% of the mass of galena is due to lead. This concept allows chemists to quantitatively assess the composition and purity of materials.

Chemical composition tells us which elements make up a compound and in what proportions. In the context of the problem, we look at the composition of the mineral galena (PbS), a natural mineral form of lead sulfide. By understanding the chemical composition, we can determine the different elements present and how they interact.

• Galena is composed of lead and sulfur in a 1:1 ratio,
• This means for every molecule of galena, there is one atom of lead and one atom of sulfur.

Physical properties and chemical behavior of compounds are impacted by their chemical composition. For example, understanding that galena is primarily composed of lead allows us to process and extract lead for various industrial applications.

A metric ton, sometimes just called a tonne, is a unit of mass commonly used in countries that observe the metric system. It is equivalent to 1,000 kilograms or approximately 2,204.62 pounds. In the exercise, the calculation of lead extraction was based on the amounts provided in metric tons. Using metric tons is particularly useful in large-scale industrial and scientific calculations because they allow for handling and interpreting large quantities of materials effortlessly. When dealing with heavy metals or ores, such as galena, it is important to use standardized units like metric tons to ensure accuracy and clarity in communication. In this problem, knowing that one metric ton of lead ore contains a specific percentage of the mineral allows us to determine how much pure lead we can extract, facilitating large-scale planning and processing.