Ways to express the concentration of solutions.

Ways to express the concentration of solutions.

​Presenter Dr. Luis Bello

Tulsa Community College

A solution is a mixture of two or more substances, where one substance is dissolved in another.

The concentration of a solution is a measure of how much of the solute (the dissolved substance) is present in a given amount of the solvent (the substance in which the solute is dissolved).

Molarity (M):

1. This is the most common way of expressing the concentration of a solution, and it is defined as the number of moles of solute per liter of solution.

2. For example, a solution with a concentration of 0.1 M NaCl contains 0.1 moles of NaCl in 1 liter of solution.

Molality

1. Molality (m): Molality is similar to molarity, but it is defined as the number of moles of solute per kilogram of solvent.

2. Molality is often used when working with solutions at high temperatures or pressures, where the volume of the solution may change significantly.

Mass Percent

1. Mass percent (% m/m): Mass percent is a way of expressing the concentration of a solution as the percentage of the mass of the solute in the total mass of the solution.

2. For example, a 10% m/m solution of glucose contains 10 grams of glucose per 100 grams of solution.

Volume Percent

1. Volume percent (% v/v): Volume percent is similar to mass percent, but it expresses the concentration of a solution as the percentage of the volume of the solute in the total volume of the solution. For example, a 20% v/v solution of ethanol contains 20 mL of ethanol per 100 mL of solution.

Mole Fraction

1. Mole fraction (X): Mole fraction is a way of expressing the concentration of a solution as the number of moles of solute divided by the total number of moles in the solution.

2. It is often used in thermodynamics and other physical chemistry calculations.

Part per million

1. Parts per million (ppm): Parts per million is a way of expressing very dilute concentrations of a solute in a solution.

2. It is defined as the number of parts of solute per million parts of solution. For example, a solution with a concentration of 10 ppm of lead contains 10 parts of lead per million parts of solution.

Multiple Choice

What is the molarity of a 0.5L sample of a solution that contains 60.0 g of sodium hydroxide (NaOH)

• 0.8 M

• 1.5M

• 3.0M

• 6.0M

Multiple Choice

What volume is needed to make a 2.45 M solution of KCl using 0.50 mol of KCl?

• 4.9 L

• 0.20 L

• 1.2 L

Multiple Choice

What is the molality of a solution made by dissolving 2 moles of NaOH in 400 grams of water?

• 5 mol/kg. solvent

• 4 mol/kg solvent

• 3 mol/kg. solvent

• 2.5 moles /kg solvent

Multiple Choice

What is the percent by mass of a solution made by dissolving 20.0 g of NaCl into 180.0 g of water?

• 10.0 %

• 11.1 %

• 80.0 %

• 20.0 %

Multiple Choice

What is the concentration, in percent by volume, of 15.3 mL of solute in 2.65 L of solution?

• 0.58%

• 0.0058%

• 5.8%

Multiple Choice

What is the mole fraction of NaOH in an aqueous solution that contains 22.8% NaOH by mass?

• a. 0.57

• b. 0.11

• c. 4.29

• d. 4.859

Multiple Choice

What is the concentration of a solution in parts per million if 0.02 grams of NaCl is dissolved in 1000 grams of solution?

• 2 ppm

• 20 ppm

• 200 pm

• 0.2 ppm

Explanation Slide...

20g / (180g+ 20g) x 100 = 10 %