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. 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

2) Calculate the mass of solute required to prepare 1 L of a 1 2) Calculate the mass of solute required to 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 Dilution Formula: M1 x V1 = M2 x V2

(Solution # 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 (Solution # 2) M1 x V1 = M2 x V2 Rearrange and Apply Equation:

0.30 M sodium hydroxide solution. V1= ? M1 = 2.00 M V2= 500 mL Diluting Solutions: 2) Find the volume of 2.00 M NaOH stock solution needed to prepare 500 mL of 0.30 M sodium hydroxide solution. V1= ? M1 = 2.00 M V2= 500 mL M2 = 0.30 M M1V1 = M2V2 V1=   V1= V1= 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

Summary: % by mass = X 100 X 100 % by volume = M1V1 = M2V2 Mol Fraction (X) Molarity (M) = Molality (m) = M1V1 = M2V2 Diluting solutions