Warm Up 3-14-18 Explain what happen to the gases inside these two cups What can you do to dissolve more sugar in water? What will happen when you add a polar compound to a nonpolar solvent? Molarity Demo plastic beads in water and then in ethanol Agenda -Turn in WS 8-3 -Notes Unit 8-4 -WS 8-4 Concentration Homework March 20 - Quiz

Notes Unit 8-4 Concentration

Concentration Concentration is the amount of the solute to solvent express in a ratio There are 4 ways to calculate concentration

Concentration Molarity 1) Molarity (M): the number of molecules per volume. Unit specific. Molarity = Moles of solute Liters of solution

Molarity Example #1 Find the molarity of a solution that has a volume of 400mL and contain 5 mol of KF #3 - How many grams of HCl do you need to create 3L of 0.5M of HCl (hydrochloric acid)? #4 - What volume of water would be required to dissolve 67 grams of Lithium Fluoride (LiF) to a concentration of 1.6 M?

Molarity Example #2 How many grams of HCl do you need to create 3L of 0.5M of HCl (hydrochloric acid)?

Concentration PPM 2) Parts per million (ppm): use for very low concentrations ppm = mass of solute x 1,000,000 mass of solution Carbon monoxide 30ppm headaches occur, 1500ppm death within 2 hours Hydrogen sulfide 100ppm lead to paralysis Nerve gas again tabun developed as an insecticide 1936, Sarin (1944) attacks nerve endings preventing them from switching off lungs muscles paralysis death within 1-10 minutes. Short shelf life degrades quickly.

Example #1 A sample of 300 g of drinking water is found to contain 38mg of lead. What is this concentration in ppm? A recent report suggests that even a blood level of 10 micrograms per decilitre can have harmful effects on children's learning and behavior (CDC, 2000).   10ug/dl is 0.1 ppm of lead

Example #2 What is the concentration of 2 grams of lead added to 500 grams of solution in ppm? 2/(500+2) because of the total mass of solution

Concentration Density 3) Density = M / V Density = mass of solute volume of solution Units: g Or g L mL

Example #1 What is the g/L of a Gatorade solution with 30mg of potassium in 240mL of water? Why do athletes drink Gatorade? And does it help? Human sweat has 0.9g/L of NaCl and 0.2g/L of potassium

Concentration Percent by Mass 4) % Mass - describes the chemical make-up of that sample as a ratio. (Sometimes abbreviate as w/w %) % Mass = Mass solute x 100 Mass of solution Similar to percent composition

Example #1 What is the percent composition of Salt when you have 25g NaCl dissolved in 50g of water?

Example #2 A 55.0 g sugar and 21g of NaCl is dissolved in 750 g of water. Find the % by mass of the sugar.

Assignments Summary: Explain the concept of concentration. How do we measure them. WS 8-4 practice due next class MUST HAVE SOME WORK DONE BEFORE LEAVING DON’T DO #11 and #12

Quiz Topics Solute vs solvent “Like dissolve like” – polarity Colloid vs Suspension “Like dissolve like” – polarity Miscible vs immiscible Solubility of solid, liquid, and gas Types of saturation Concentration equations – memorize only doesn’t have to calculate yet