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Concentration of solutions

Concentration of solutions. CONCENTRATED = Lots of solute in the solution DILUTE = Not much solute in the solution. Ways to express concentration numerically. Molarity % by Mass % by Volume Parts per million. MOLARITY. Molarity = # of moles of solute in 1 liter of solution.

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Concentration of solutions

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  1. Concentration of solutions CONCENTRATED = Lots of solute in the solution DILUTE = Not much solute in the solution

  2. Ways to express concentration numerically • Molarity • % by Mass • % by Volume • Parts per million

  3. MOLARITY

  4. Molarity = # of moles of solute in 1 liter of solution

  5. See Table T

  6. Molarity Problems What is the molarity of a solution of NaOH if there are 4 moles of NaOH dissolved water to make 1 liter of solution? 4 moles = 4 M 1 liter

  7. Molarity Problems What is the molarity of a solution of NaOH if there are 4 moles of NaOH dissolved water to make 2 liters of solution? 4 moles = 2 M 2 liter

  8. Molarity Problems What is the molarity of a solution of NaOH if there are 2 moles of NaOH dissolved water to make 6 liters of solution? 2 moles = .33 M 6 liters

  9. Molarity Problems What is the molarity of a solution of NaOH if there are 2 moles of NaOH dissolved water to make .5 liters of solution? 2 moles = 4 M .5 liters

  10. Molarity Problems What is the molarity of a solution of NaOH if there are 40 grams of NaOH dissolved water to make 1 liters of solution? First, convert grams to moles: Na = 23 g/mol O = 16 g/mol so 40 g = 1 mole H = 1 g/mol 40 g/mole GFM

  11. Molarity Problems What is the molarity of a solution of NaOH if there are 40 grams of NaOH dissolved water to make 1 liters of solution? 1 moles = 1 M 1 liters

  12. Molarity Problems What is the molarity of a solution of NaOH if there are 80 grams of NaOH dissolved water to make 1 liters of solution? 80g/40g/mol = 2 moles 2 moles = 2 M 1 liters

  13. Molarity Problems What is the molarity of a solution of NaOH if there are 3.6 grams of NaOH dissolved water to make 2 liters of solution? 3.6g/40g/mole = 0.09 moles 0.09 moles = 0.045 M 2 liters

  14. In General…. Concentrations < 1M are considered weak, or dilute Concentrations > 1M are considered strong, or concentrated Always know the concentration of your solution before you use it!!!! (read the label)

  15. Can you…. Rearrange the molarity equation to solve for moles? Molarity = Moles Liter moles = ?

  16. Can you…. Rearrange the molarity equation to solve for moles? Molarity = Moles Liter moles = Liter x Molarity

  17. Can you…. Rearrange the molarity equation to solve for Liters? Molarity = Moles Liter Liters = ?

  18. Can you…. Rearrange the molarity equation to solve for Liters? Molarity = Moles Liter Liters = Moles Molarity

  19. Example How many moles of NaOH do you have if you have 3 liters of a 0.5M NaOH solution? Moles = Molarity x Liters Moles = 0.5M x 3 liters Moles = 1.5

  20. % Mass Uses the same formula as % composition (See Table T) Percent mass = mass of part x 100 Mass of whole

  21. % Mass What is the % mass of NaOH if 2.5 g of NaOH are added to 50 g of water? Percent mass = mass of part (solute) x 100 Mass of whole (solution) % mass = 2.5g x 100 (2.5 + 50g) % mass = (2.5 / 52.5) x 100 = 4.76% solution

  22. % Volume Uses the same formula as % composition (See Table T) Percent volume = volume of part x 100 volume of whole

  23. % Volume What is the % volume of NaOH if 20 ml of NaOH are added to 300 ml of water? Percent volume = volume of part (solute) x 100 volume of whole (solution) % volume = 20 ml x 100 (20 ml + 300 ml) % volume = (20 / 320) x 100 = 6.25% solution

  24. Parts per million ppm = grams solute x 1,000,000 grams solution This is used when the amount of solute is very very small

  25. Parts per million ppm = grams solute x 1,000,000 grams solution .0043 g of oxygen gas dissolve in 100 ml of water at 20 degrees celsius. What is the concentration in ppm?

  26. Parts per million ppm = .0043g x 1,000,000 (100 g + 0.0043g) Concentration = 43 ppm

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