1. Dilution Problems

2. 2-step Molarity Problems Study them because that’s the process we need to go through if we are making a solution from a solid solute. For example, if I want a 1 M NaCl solution, I have to weigh out 1 mole or 58.5 grams of NaCl and add water until I have 1 Liter of solution.

3. Dilution Problems Sometimes we make a dilute solution from a very concentrated solution.

4. Dilution & Evaporation Amount of solvent changes. Amount of solute is constant.

5. A portion of the original solution is diluted. number of solute particles What can you say about the number of solute particles in pictures b and c? It’s the same!

6. Molarity Molarity = # of moles of solute Liters of solution Molarity X Liters of solution = # of moles of solute

7. Amount of solute is constant Amount of solute in concentrated solution = Amount of solute in dilute solution

8. Molarity C X Volume C = Molarity D X Volume D M C X V C = M D X V D

9. Dilution problems Important to pair up the molarity and volumes correctly. The more concentrated molarity is the larger number. The dilute molarity is the smaller number.

10. How much 0.25 M NaCl solution can be made from 1.0 Liter of 1.0 M NaCl solution? Identify the variables M D = 0.25 V D = X M C = 1.0 M V C = 1.0 Liter Plug into equation (0.25)X = (1.0)(1.0) 0.25 X =1.0 X = 4.0 4.0 Liters of 0.25 M NaCl can be made.

11. Dilution problems Twist: Sometimes they want to know how much water you have to add to the concentrated solution to get the dilute solution. The dilution formula gives the volume of the dilute solution and the volume of the concentrated solution, NOT the volume of water. V D = V C + V H2O so V D – V C = V H2O

12. How much water must be added to 0.5 Liters of 3.0 M NaCl to make 1.0 M NaCl? Identify Variables M C = 3.0 M V C = 0.5 Liters M D = 1.0 M V D = X Plug into equation (1.0)X = (3.0)(0.5) X = 1.5 Liters = V D That’s NOT how much water you need to add. That’s the final volume!

13. Finding the water you add… End up with 1.5 liters of dilute solution. Started with 0.5 liters of concentrated solution. The difference, 1.0 liter, is how much water must be added.