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Solutions & Solubility

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.

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Solutions & Solubility

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  1. Solutions & Solubility Concentration

  2. 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

  3. Concentrations of Solutions 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

  4. Practice ProblemsTitle: Molarity ProblemsYou 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 NH4NO3? 4. How many moles of solute are in 250 mL of 2.0M CaCl2? How many grams of CaCl2 is this?

  5. Concentrations of Solutions 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 M1× V1 = M2 × V2 • M1 & V1 are initial and M2 & V2 are final of the SAME solution • Volumes can be in L or mL, as long as the same units are used for both V1 & V2

  6. Practice ProblemsTitle: Dilution ProblemsYou do not have to write the problem. You MUST show your work. You have the following stock solutions available: 2.00M NaCl, 4.00M KNO3 and 0.50M MgSO4. Calculate the volumes you must dilute to make the following solution. 5. 250.0 mL of 0.300M NaCl 6. 75.0 mL of 0.200M KNO3 7. 5.0 L of 0.2M MgSO4

  7. Concentrations of Solutions 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) Must be the same unit: mL or L Must be this unit

  8. Practice ProblemsTitle: Percent Solution ProblemsYou 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 75g K2SO4 in 1500mL of solution? 9. A bottle of hydrogen peroxide antiseptic is labeled 3.0% (v/v). How many mL H2O2 are in a 400.0 mL bottle of this solution? 10. Calculate the grams of solute required to make 250 mL of 0.10% MgSO4 (m/v).

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