Molarity (M): State the ratio between the number of moles of solute & the volume of solution (in liters). Molarity (M) =

Example: Find the molarity of 500 mL of a solution which contain 60 g of NaOH dissolved in water. Solute= 60 g NaOH ÷ 40 g/mol = 1.5 mol Solution= 500 mL = 0.5 L Molarity (M) = = = 3.0 mol/L or 3.0 molar

Preparing Molar Solutions: How could you prepare 1 L of a 1.5 M of magnesium chloride solution? M = moles of solute = molarity x liters of solution = 1.5 mol/L x 1 L = 1.5 mol MgCl2 mass of MgCl2 = = 1.5 mol x 95 g/mol = 142.5 g Must be dissolved in water up to 1 L of solution. (Use a volumetric flask)

Dilution: Dilution is adding extra solvent to decrease the concentration of a solution The amount of solute stays the same, but the concentration decreases Dilution Formula: M1 x V1 = M2 x V2

Example – What Volume of 12. 0 M KCl is needed to prepare 5. 00 L of 1 Example – What Volume of 12.0 M KCl is needed to prepare 5.00 L of 1.50 M KCl Solution? Initial Solution (1) Final Solution (2) Concentration 12.0 M 1.50 M Volume ? L 5.00 L M1 x V1 = M2 x V2 Rearrange and Apply Equation:

Making a Solution by Dilution Dilute 0.625 L of 12.0 M solution to 5.00 L

Diluting Solutions: Find the volume of 2.00 M NaOH stock solution needed to make 0.5 L of 0.3 M sodium hydroxide solution. V1= ? M1 = 2.00 M V2= 0.5 L M2 = 0.3 M M1V1 = M2V2 V1= V1= V1= 0.075 L or 75 mL

Molality (m): State the ratio between the number of moles of solute & the mass of solvent (in kg). Molality (m) =

Example: Find the molality of a solution made by adding 4.5 g of NaCl to 100 g of water. Solute= 4.5 g NaCl ÷ 58.5 g/mol = 0.077 mol Solvent= 100 g = 0.1 kg Molality (m) = = = 0.77 mol/kg or 0.77 mol.kg-1