1. Can U Concentrate? We have been talking a lot about solutions… –What is the solvent? –What is the solute? –What affects the rate of solution? But what we haven’t covered is concentration.

2. What is Concentration? It is an indication of how much solute is in a solvent. It is a way for us to quantify how dilute or concentrated a solution is. Why is it important to know concentration? Well let’s look at a real life example…

3. DUI’s A cop patrolling down by the beach notices a guy being very loud and obnoxious. He suspects that he is intoxicated (drunk) but his friends insist that he always acts this way

4. The cop can’t just arrest a guy for being obnoxious, so what can he do? He can give him a breathalyzer test which determines his –BAC Blood Alcohol Content This will give him a measurement on which to base his assessment of this guy’s intoxication level.

5. What is BAC? BAC (blood alcohol content) is an indication of what % of a person’s blood volume is made up of alcohol, or what is the alcohol concentration of their blood. A BAC of 0.08% is considered legally drunk (0.01% if under 21) A BAC of 0.37% = dead

6. By the way A DUI will cost a teenager about $45,000 Cost of annual auto insurance increase over 13 years $40,000 DUI classes$650 Towing and storage fee ($137 a day)$685 (at least 5 days) Fines and attorney fees$4,000 DMV reinstatement fee$100 Estimated Minimum total$45,435

7. Solutions Calculations % By Volume % By Mass Now back to our regularly scheduled program….

8. Objectives To set up and solve % by Mass and % by Volume calculations To use the density of water to convert between mass and volume of a solvent

9. % Calculations You can use % by mass to describe how much solid solute has dissolved in a liquid or solid solvent. All of your numbers need to be in same unit of mass (g, kg, mg etc.) You can use % by volume to describe how much liquid solute is dissolved in a liquid solvent. All of your numbers need to be in the same unit of volume (L, mL etc.)

10. Remember that the denominator has the total amount of solution, volume solvent + volume of solute! What is the concentration of 75 mL KBr in 2500 mL of water? % Vol = 2.90 %

11. Be careful!! The denominator must have the total mass of the solution… g solute + g solvent! Ex: What is the concentration of a solution that has 5 g solute dissolved in 100 g solvent? % Mass = 4.76 %

12. More practice… What is the concentration of 20 g KBr in 600 g of water? % Mass = 3.23 %

13. 1 More thing… Sometimes, the problems will assume that you know the density of water in order to calculate % mass. Density of water = 1g / 1 mL You can use the density as a conversion factor How much will 600 mL of water weigh? 600 mL 1 mL 1 g = 600 g

14. % Calculation w/ Density Practice What is the concentration of 15 g HBr dissolved in 600 mL of water? 600 mL 1 mL 1 g = 600 g % Mass = 2.40 %

15. More Practice How much water is needed to make a 15% solution with 5g of solute? X = 28.33 g (15)(5 + x) = 5 * 100 (15)(5 + x) = 500 15 15 5 + x = 33.33

16. Solutions Calculations Parts Per Million (ppm)

17. Objectives To explain what ppm or parts per million means and when to use it.

18. PPM Parts per millions is a way to calculate concentrations when the amount of solute is very small.