1. Ch. 12.3 Concentration of a Solution The concentration of a solution is a measure of the amount of solute in a given amount of solvent or solution. Chemists commonly use several different ways to quantitatively express the concentration of a solution. These include:  Percent Composition by mass  Parts per million / Part per billion  Molarity (M)  Molality (m)

2. Percent Composition by Mass Sometimes the amount of solute present in the solution is expressed as a percent by mass. grams of solute % Composition = ------------------------- x 100 grams of solution Remember: solution is the solute and solvent together

3. Percent Composition Sample Problems 1.What is the percent composition of a solution that contains 115 g NaCl dissolved in 500 g of H 2 O? 2.How many grams of KMnO 4 are needed to make 500 g of a 12.0% KMnO 4 solution?

4. Parts per Million (ppm) and Parts per Billion (ppb) ppm = mass of solute in solution total mass of solution  10 6 Parts per Million (ppm) Parts per Billion (ppb) ppb = mass of solute in solution total mass of solution  10 9

5. What Do You Think? A 900.0 g sample of sea water is found to contain 0.0067 g Zn. Express this concentration in ppm.

6. Molarity (M) Molarity (M) is the number of moles of solute per liter of solution. moles of solute (mol) Molarity (M) = -------------------------------- liters of solution (L) Video

7. Molarity Sample Problems 1.What is the molarity of a 0.500 L sample of solution that contains 60.0 g of sodium hydroxide (NaOH)? 2.How many grams of sodium chloride (NaCl) are required to prepare 250.0 mL of a 3.00 M solution?

8. Molality (m) Molality is the concentration of a solution expressed in moles of solute per kilogram of solvent. moles of solute (mol) Molality (m) = ----------------------------------- kilogram of solvent (kg)

9. Molality Sample Problem 1.A solution was prepared by dissolving 17.1 g of glucose, C 6 H 12 O 6, in 275 g of water. What is the molality (m) of this solution?

10. Dilutions When preparing dilutions, you use the following equation. –M 1 V 1 =M 2 V 2 As volume goes up, molarity goes down. You have diluted the solution. As volume goes down, the amount of solute in solution increases in concentration. Think of diluting your kool aid.

11. Dilutions practice 1.If I have 340 mL of a 0.5 M NaBr solution, what will the concentration be if I add 560 mL more water to it? 2.If I dilute 250 mL of 0.10 M lithium acetate solution to a volume of 750 mL, what will the concentration of this solution be?

12. Wrapping It Up Reflect on what you have learned concerning the today’s topic. Respond to the following… –What is the most important thing you learned today? –What is one question you would still like answered? –What is a way what you have learned today connects with what you knew before?