Question

How do we define the mass percent composition of a solution? Give an example of a solution, and explain the relative amounts of solute and solvent present in the solution in terms of the mass percent composition.

Short answer

The mass percent composition of a solution is defined as the mass of the solute divided by the total mass of the solution, multiplied by 100. In a saline solution with 20 grams (g) of table salt (NaCl) dissolved in 80 grams (g) of water, the mass percent composition is calculated as follows: Mass Percent Composition = \(\frac{20 \, g}{100 \, g} \times 100\) = 20%. The saline solution has a 20% mass percent composition of table salt, while the remaining 80% is water.

Step-by-step solution

Define Mass Percent Composition

Mass percent composition (also called weight percent or mass fraction) is a way of expressing the concentration of a solute in a solution. It represents the mass of a solute divided by the total mass of the solution, multiplied by 100 to get the percentage. The formula for mass percent composition can be written as: Mass Percent Composition = \(\frac{Mass \, of \, Solute}{Mass \, of \, Solution} \times 100\) Now we'll provide an example of a solution and demonstrate how to calculate the mass percent composition.

Choose a Solution and Identify the Solute and Solvent

Let's consider a solution of table salt (sodium chloride, NaCl) dissolved in water to create a saline solution. In this example, table salt is the solute and water is the solvent.

Define the Masses of the Solute and Solvent

Let's assume we have 20 grams (g) of table salt (NaCl) dissolved in 80 grams (g) of water. Mass of solute (NaCl) = 20 g Mass of solvent (water) = 80 g

Calculate the Total Mass of the Solution

To determine the mass percent composition, first calculate the total mass of the solution by adding the mass of the solute (NaCl) to the mass of the solvent (water): Mass of solution = Mass of solute + Mass of solvent Mass of solution = 20 g (NaCl) + 80 g (water) Mass of solution = 100 g

Apply the Mass Percent Composition Formula

Now, apply the mass percent composition formula using the given mass of solute and mass of solution: Mass Percent Composition = \(\frac{Mass \, of \, Solute}{Mass \, of \, Solution} \times 100\) Mass Percent Composition = \(\frac{20 \, g}{100 \, g} \times 100\)

Calculate the Mass Percent Composition

Finally, calculate the mass percent composition of the solute in the solution: Mass Percent Composition = \(\frac{20 \, g}{100 \, g} \times 100\) = 20% In this example, the mass percent composition of table salt (NaCl) in the saline solution is 20%. This means that 20% of the total mass of the solution is made up of table salt, while the remaining 80% is water.