1. PP. 398 - 405 8.6 & 8.7 Concentration and Preparing Dilutions

2. Concentration Concentration = the amount (n) of solute per unit volume of solution This can be represented by the following equation: Amount concentration= amount of solute (mol) Volume of solution (L) c= n V The units of concentration are mol/L

3. Chemistry Mole

4. Example 1 Sulfuric acid is a solution of hydrogen sulphate, H 2 SO 4. What is the concentration of a 200 mL sample sulphuric acid if it contains 44g of hydrogen sulphate?

5. Example 2 What mass of sodium chloride is needed to make 100 mL of a 0.5 mol/L solution?

6. Preparing Solutions There are 2 ways to prepare aqueous solutions that are needed for many chemical applications: 1) From a solid 2) By dilution

7. Preparing Solutions From a Solid A solution of a known concentration is called a standard solution. These solutions are prepared in volumetric flasks, which contain a certain volume at a specific temperature (usually 20 degrees) Making up a standard solution: http://www.youtube.com/watch?v=cckAwavEKA0

8. Preparing Solutions by Dilution A stock solution is a concentrated solution that is to be diluted to a lower concentration before use. Dilution is the process of reducing the concentration of a solution by adding more solvent. Equipment to use: Volumetric pipette—delivers a fixed volume of solution. Very precise. Graduated pipette – has volume markings/gradations. Not as precise.

9. Dilution Calculations We can calculate the exact volume needed when preparing dilute solutions. Equation: c i v i = c f v f or c 1 v 1 = c 2 v 2 i or 1= concentration of initial/first solution f or 2= concentration of final/second solution

10. Example 3 What is the final concentration when 4.5 L of 3.0 mol/L car battery acid is diluted to 20.0 L?

11. Homework Read pp. 398 – 405 Answer the following questions:  p. 402 # 1 – 9  p. 405 # 1 – 7