Solutions Solubility Concentration Concentrations of Solutions l l

Solutions & Solubility Concentration

Concentrations of Solutions l l Concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solution. Dilute solution – contains a low concentration of solute. Concentrated solution – contains a high concentration of solute. Molarity (M) – number of moles of a solute dissolved per liter of solution l a. k. a. molar concentration

Concentrations of Solutions Molarity l Calculate the number of moles in 1 L of the solution Molarity (M) = moles of solute liters of solution Example 1 Calculate the molarity when 2 mol of glucose is dissolved in 5 L of solution, divide the number of moles by the volume in liters. 2 mol glucose 5 L solution = 0. 4 mol/L = 0. 4 M

Practice Problems Title: Molarity Problems You do not have to write the problem. You MUST show your work. 1. A solution has a volume of 2. 0 L and contains 36. 0 g of glucose. If the molar mass of glucose is 180 g, what is the molarity of the solution? 2. A solution has a volume of 250 m. L and contains 0. 70 mol Na. Cl. What is its molarity? 3. How many moles of ammonium nitrate are in 335 m. L of 0. 425 M NH 4 NO 3? 4. How many moles of solute are in 250 m. L of 2. 0 M Ca. Cl 2? How many grams of Ca. Cl 2 is this?

Concentrations of Solutions Making Dilutions l l You can make a solution less concentrated by diluting it with solvent. A dilution reduces the moles of solute per unit volume, however, the total moles of solute in solution does not change Moles of solute before dilution = moles of solute after dilution M 1 × V 1 = M 2 × V 2 l M 1 & V 1 are initial and M 2 & V 2 are final of the SAME solution l Volumes can be in L or m. L, as long as the same units are used for both V 1 & V 2

Practice Problems Title: Dilution Problems You do not have to write the problem. You MUST show your work. You have the following stock solutions available: 2. 00 M Na. Cl, 4. 00 M KNO 3 and 0. 50 M Mg. SO 4. Calculate the volumes you must dilute to make the following solution. 5. 250. 0 m. L of 0. 300 M Na. Cl 6. 75. 0 m. L of 0. 200 M KNO 3 7. 5. 0 L of 0. 2 M Mg. SO 4

Concentrations of Solutions Percent Solutions Must be the same unit: m. L or L l If both solute & solvent are liquids Percent by volume (% v/v) = volume of solute × 100% solution volume l If a solid is dissolved in a liquid Percent mass / volume (% m/v) = mass of solute (g) × 100% solution volume (m. L) Must be this unit

Practice Problems Title: Percent Solution Problems You do not have to write the problem. You MUST show your work. 8. What is the concentration, in percent (m/v), of a solution with 75 g K 2 SO 4 in 1500 m. L of solution? 9. A bottle of hydrogen peroxide antiseptic is labeled 3. 0% (v/v). How many m. L H 2 O 2 are in a 400. 0 m. L bottle of this solution? 10. Calculate the grams of solute required to make 250 m. L of 0. 10% Mg. SO 4 (m/v).