2. 1. General Terms a. concentratedLots of solute dissolved in the solvent b. diluteLittle solute in the solvent 2. Specific terms a. Percent by mass Describes the mass of solute in the mass of the solution Mass of solute Mass of solution X 100

3. Examples 1. What is the percent mass of a solution if 100.0 g of solution contains 30.0 g of NaCl? 2. If we add 25.0 g of KCl to 80.0 g of water, what is the percent by mass of the solution? 3. If we want to make a 20.0% solution by mass, how much KBr must we add to make 45 g of solution? Mass of solute Mass of solution X 100 30 100 X 10030.0% To get the mass of the solution, we must add solute + solvent! Mass of solute Mass of solution X 100 25.0 105.0 X 10023.8% Mass of solute Mass of solution X 100 X 45 X 1009.0 g20.0 =

4. b. Parts per million (ppm) Used for very small concentrations. % = parts per hundred Ppm = parts per million Mass of solute Mass of solution X 1,000,000 10 ppm NH 3 10 g of NH 3 for every 1,000,000 g of solution Example 1. We determined that the air contains 0.300 g of CO 2 for every 5,000.0 g of air. What is the concentration in ppm? 2. The legal amount of methyl isocyanate is 0.020 ppm. How many grams of this chemical can we find in 3300 g of air? Mass of solute Mass of solution X 1,000,000 Mass of solute Mass of solution X 1,000,000 0.30 5,000 X 1,000,00060.0 ppm X 3300 X 1,000,000 0.000066 g0.020= 6.6 x 10 -5 g

5. c. Molarity Specific measurement of concentration Moles of solute dissolved in one liter of solution 6.0 M HCl6.0 moles of HCl dissolved in H 2 O to make one liter Formula Molarity (M) = moles of solute liters of solution

6. Remember, check to see if you have moles or grams, and if you are using liters or milliliters. Molarity Practice A. What is the molarity of a solution if we add 8.00 moles of LiCl to 2.00 L of water? M = moles liters M = 8.00 moles 2.00 L M = 4.00 M B. If we have 500.0 g of HCl dissolved to make 2.00 L of solution, what is the molarity? Must change g to moles first! 500.0 g x (36.46 g/mole) 13.71 moles M = moles liters M = 13.71 moles 2.00 L M = 6.85 M

7. C. If we have 36.46 g of HCl in 100.0 ml of solution, what is the molarity? Must change ml in to L! 36.46 g x (36.46 g/mole) 1.000 mole 100.0 ml = 0.1000 L M = moles liters M = 1.000 moles 0.1000 L M = 10.00 M

8. M – moles liters M = 1.00 moles 2.50 L