In \(75 \mathrm{~g}\) of a \(12.0 \%\) by mass solution of \(\mathrm{BaCl}_{2}\) (a) how many grams of solute are present? (b) how many grams of solvent are present?

Understanding the mass of solute is a foundational concept in chemistry, especially in the context of solution preparation. The mass of solute refers to the weight of the substance that is dissolved in a solvent to form a solution. For instance, if we dissolve table salt (NaCl) in water to create a saltwater solution, the table salt is the solute.

When calculating the mass of solute from a given percentage by mass solution, like a 12.0% BaCl₂ solution, we calculate the portion of the solution mass that is made up by the solute. In the provided example, we see that the solution has a mass of 75 g, and the BaCl₂ makes up 12% of this mass. Using the formula:

While the mass of solute is crucial, it's equally important to grasp the concept of mass of solvent. The mass of solvent in a solution is the weight of the liquid (or gas, in some cases) that dissolves the solute. Continuing with the previous example, if water is used to dissolve BaCl₂, water would be our solvent.

Calculating the mass of solvent is straightforward once you know the mass of the solute and the total mass of the solution. It is simply the remainder of the total mass after subtracting the mass of the solute. This can be understood as:

The concentration calculation is a fundamental tool for scientists and students alike, enabling them to understand the composition of solutions. Concentration can be expressed in various ways, such as molarity, molality, and percentage by mass.

In our specific case, we use the percentage by mass to express concentration. It is defined as the mass of the solute divided by the total mass of the solution, multiplied by 100%. It helps in determining how much of a substance is present in a solution compared to the total mixture. By following the provided steps, we learned how to calculate both the mass of solute, which is essential for finding the percentage, and the mass of solvent, which allows us to determine the solution's remaining composition. These calculations are central to preparing solutions with desired properties in labs and various industries.

It's important to note that accurate concentration calculations require precise measurements and a clear understanding of the formulas involved. For educational exercise and practical applications, understanding and being able to compute the concentration are key skills in chemistry.