Solutions & Solubility Concentration

Concentrations of Solutions 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 a.k.a. molar concentration

Molarity 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 Concentrations of Solutions

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 2.0L and contains 36.0g 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 mL and contains 0.70 mol NaCl. What is its molarity? 3. How many moles of ammonium nitrate are in 335 mL of 0.425M NH 4 NO 3 ? 4. How many moles of solute are in 250 mL of 2.0M CaCl 2 ? How many grams of CaCl 2 is this?

Making Dilutions 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 M 1 & V 1 are initial and M 2 & V 2 are final of the SAME solution Volumes can be in L or mL, as long as the same units are used for both V 1 & V 2 Concentrations of Solutions

You have the following stock solutions available: 2.00M NaCl, 4.00M KNO 3 and 0.50M MgSO 4. Calculate the volumes you must dilute to make the following solution mL of 0.300M NaCl mL of 0.200M KNO L of 0.2M MgSO 4 Practice Problems Title: Dilution Problems You do not have to write the problem. You MUST show your work.

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

8. What is the concentration, in percent (m/v), of a solution with 75g K 2 SO 4 in 1500mL of solution? 9. A bottle of hydrogen peroxide antiseptic is labeled 3.0% (v/v). How many mL H 2 O 2 are in a mL bottle of this solution? 10. Calculate the grams of solute required to make 250 mL of 0.10% MgSO 4 (m/v). Practice Problems Title: Percent Solution Problems You do not have to write the problem. You MUST show your work.