Aim: How do you express concentration of a solution DO NOW: On a separate sheet of paper, tell me what you did over break. Will be collected in 3 min. Homework: Do worksheet. Must show work on the bottom of the page. Quiz Wed.

Vocabulary Concentration: a measurement of the amount of solute that is dissolved in a given quantity of solvent Concentrated solution: a solution containing a large amount of solute Dilute solution: a solution that contains a small amount of solute

Units of Concentration (Table T) ways to express the amount of solute in solution (concentration) Mass or Volume percent of solute Parts per million (ppm) Molarity

Units of Concentration Percent volume % volume = volume solute (ml) x 100 volume solution (ml) Percent mass % mass = mass solute (g) x 100 mass solution (g) Solution = solvent + solute

Units of Concentration Example 1: What is the percent by volume concentration of a solution in which 75.0 ml of ethanol is diluted to a volume of 250.0 ml?

Units of Concentration Example 2: What volume of acetic acid is present in a bottle containing 350.0 ml of a solution which measures 5.00% concentration?

Units of Concentration Example 3: Find the percent by mass in which 41.0 g of NaCl is dissolved in 331 grams of water.

Parts per million (ppm) ppm solute = (mass solute/total solution mass) x 106

ppm Example Example – In the United States and Canada, drinking water cannot contain more than 5 x 10-4 mg of mercury per 1x 103 mg of sample of solution. In parts per million what would that be?

Questions An aqueous solution has 0.0070 gram of oxygen dissolved in 1000. grams of water. Calculate the dissolved oxygen concentration of this solution in parts per million. Your response must include both a correct numerical setup and the calculated result.

Molarity (M) M = mols of solute /Liters of solution Remember moles = given mass x (1 mol/ molar mass) Formula from Table T M = mols of solute /Liters of solution Example – if 40 g of NaOH is dissolved in water to prepare 0.5 L of solution, what is the molarity?

M= molarity (conc.) n= moles of solute L = liters of solution n M L

Question How many moles of solute are contained in 0.2L of 1M solution?

Challenge Question Find the volume of a 0.75 M solution if it contains 39 grams of potassium hydroxide.

Molecules vs. Ionic Compounds in Aqueous solutions Some molecular compounds dissolve but do not dissociate into ions. C6H12O6(s) (glucose)  C6H12O6 (aq) 1 mole of sugar gives 1 mole of sugar when dissolved in water

Molecules vs. Ionic Compounds in Aqueous solutions Many ionic compounds dissociate into independent ions when dissolved in water NaCl (s)  Na+(aq) + Cl-(aq) 1 mole of NaCl solid gives 1 mole of sodium ions and 1 mole of chloride ions when dissolves (total of 2 moles of dissolved particles). MgCl2 (s)  Mg+2(aq) + 2Cl-(aq) Total of 3 moles of dissolved particles