Preparing a Molar Solution How many grams of sucrose (C12H22O11) is needed to prepare one liter of a 1.50 M solution? You’ll need the molar mass of sucrose: 1.5 mol 342 g _____________ X ___________ = 513 g / liter 1 liter 1 mol

Preparing a Molar Solution How many grams of sucrose (C12H22O11) is needed to prepare 100 mL of a 1.50 M solution? 1.5 mol 342 g _____________ X ___________ = 513 g / liter 1 liter 1 mol 1 L 513 g 100 mL X __________ X _____________ = 51.3 g 1000 mL 1 L

Diluting Solutions Many solutions (acids) come in a concentrated liquid form called a stock solution To dilute this solution, you add more solvent (usually water or alcohol) The amount of solute does not change, so the amount of solution SO M1V1 = M2V2

Diluting Solutions What volume in milliliters of 2.00M calcium chloride (CaCl2) would you use to make .50 L of .300 M calcium chloride solution? .50 L X 1000 mL/1 L = 500 mL M1V1 = M2V2 2.00M x V1 = .300M x 500 mL V1 = .300M x 500 mL / 2.00M V1 = 75 mL

Mole Fraction Another way to express concentration Need to know the number of moles of solute and solvent Abbreviated as X Xa = mole fraction of solvent = na / na + nb Xb = mole fraction of solute = nb / na + nb

Mole Fractions What is the mole fraction of water in an HCl solution containing 62.5% water and 37.5% HCl by mass? 62.5 g x 1mol / 18.02 g = 3.47 mol H2O 37.5 g x 1mol / 36.46 g = 1.03 mol HCl na / na + nb 3.47 mol H20 / 1.03 mol HCl + 3.47 mol H20 na = .771