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Solutions

Solutions. Classification of Matter. Solutions are homogeneous mixtures. Solute. A solute is the dissolved substance in a solution. Salt in salt water. Sugar in soda drinks. Carbon dioxide in soda drinks. Solvent. A solvent is the dissolving medium in a solution. Water in salt water.

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Solutions

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  1. Solutions

  2. Classification of Matter Solutions are homogeneous mixtures

  3. Solute A solute is the dissolved substance in a solution. Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Solvent A solvent is the dissolving medium in a solution. Water in salt water Water in soda

  4. Solvents

  5. Saturation of Solutions • A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated. • A solution that contains less solute than a saturated solution under existing conditions is unsaturated.

  6. Concentrated vs. Dilute

  7. Suspensions and Colloids Suspensions and colloids are NOT solutions. Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. Colloids: The particles intermediate in size between those of a suspension and those of a solution.

  8. Solubility Trends • The solubility of MOST solids increases with temperature. • The rate at which solids dissolve increases with increasing surface area of the solid. • The solubility of gases decreases with increases in temperature. • The solubility of gases increases with the pressure above the solution.

  9. Therefore… Solids tend to dissolve best when: • Heated • Stirred • Ground into small particles Gases tend to dissolve best when: • The solution is cold • Pressure is high

  10. Calculations of Solution Concentration Concentration - A measure of the amount of solute in a given amount of solvent or solution Grams per liter - the mass of solute divided by the volume of solution, in liters Molarity - moles of solute divided by the volume of solution in liters Parts per million – the ratio of parts (mass) of solute to one million parts (mass) of solution Percent composition - the ratio of one part of solute to one hundred parts of solution, expressed as a percent

  11. Molarity The concentration of a solution measured in moles of solute per liter of solution. mol= M L

  12. Molality The concentration of a solution in moles of solute per kilogram of solvent. mol= m kg Since the most common solvent, water, has a density of 1 kg/L, one kilogram of water is the same as one liter of water!

  13. Calculating the molarity • If you have 2 moles of glucose in 8 liters of solution what is the molarity of the solution? Molarity= moles per liter Molarity = 2moles / 8 liters =0.25 M

  14. Calculating the molarity 2) If you have 6 moles of glucose in 4 liters of solution what is molarity of this solution? 3) If water is added to 2 mol of glucose to give 5L of solution what is its molarity? 4) A salt solution has a volume of 250ml and contains 0.70mol of NaCl. What is the molarity of the solution?

  15. Calculating the molarity Molarity = moles/liter In the problem we have 250 ml of solution Convert this to liters 250ml/1000ml =0.250L Now calculate the molarity 0.7mol = 2.8 M 0.250L

  16. Calculating the molarity A saline solution contains 0.90 g of NaCl per 100 ml of solution. What is its molarity? Molarity is moles per liter. Convert the concentration to moles per liter. Start with the gram formula mass of NaCl 23.0g+35.5g=58.5g

  17. Molarity contn Now calculate the moles of NaCl We know------1 mole NaCl contains 58.5g How many moles would be present in 0.90g 0.90 x 1.0mole = 0.015 mole 58.5 g Now convert mol per 100ml to mol per liter Molarity=Moles/liter=0.015/0.1000= 0.15M

  18. Calculating grams of solute How many grams of solute are present in 1.5L of 0.20M Na2SO4? Rearrange the equation Liters of solution x molarity =moles of solute Substitute the known in the equation 1.5L x 0.20 =0.30 mol

  19. Calculation contn To determine the weight of solute, multiply the number of moles of Na2SO4 by its mass 1.0 mol contains 142.1g 0.30mol will contain ? 0.30 x 142.1g = 42.6 g 1.0 mol

  20. Problems Find the molarity of the following 1)18 grams of NaCl is dissolved in enough water to make 1 liter of solution 2) 0.500 grams of glucose, C6H12O6 is dissolved in enough water to make 0.750 liters of solution 3) 1.45 grams of KCl is dissolved in enough water to make 450 mL of solution 4) 250 grams of KNO3 is dissolved in enough water to make 10 2 liters of solution 5) 0.002 grams of MgCl2 is dissolved in enough water to make 10 mL of solution

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