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# Lecture19222

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### Transcript of "Lecture19222"

1. 1. The Properties of Mixtures: Concentration Lecture 19
2. 2. Concentration is the measure of how much of a given substance there is mixed with another substance.
3. 3. Concentration applies to any sort of chemical mixture, but most frequently to homogeneous solutions.
4. 4. Concentration = amount or mass or volume of solute = -------------------------------------------------- amount or mass or volume of solution or solvent
5. 5. Concentration = amount or mass or volume of solute = -------------------------------------------------- amount or mass or volume of solution or solvent
6. 6. Molarity (M) = amount (mol) of solute ----------------------------------- volume (L) of solution
7. 7. Concentration = amount or mass or volume of solute = -------------------------------------------------- amount or mass or volume of solution or solvent
8. 8. Molality (m) = amount (mol) of solute ------------------------------------- mass (kg) of solvent
9. 9. A sample problem on calculating molality.
10. 10. Another sample problem <ul><li>What is the molality of a solution prepared by dissolving 339.8 g of silver nitrate in 4000. g of water? </li></ul><ul><li>Amount of AgNO 3 =339.8/169.91 = 2.000 mol </li></ul><ul><li>Mass of water=4.000 kg </li></ul><ul><li>Molality of solution= 2.000/4.000=0.500 m AgNO 3 </li></ul>
11. 11. Another sample problem <ul><li>What mass of sodium phosphate is needed to prepare 0.750 m solution by dissolving it in 800. g of water? </li></ul><ul><li>Mass of water=0.800 kg </li></ul><ul><li>Amount of Na 3 PO 4 =0.750/0.800=0.938 mol </li></ul><ul><li>Mass of Na 3 PO 4 = 0.938x163.94=154 g </li></ul>
12. 12. Another sample problem <ul><li>What mass of water is needed to prepare 0.250 m solution by dissolving 1 kg 382 g of potassium carbonate? </li></ul><ul><li>Mass of K 2 CO 3 =1382 g </li></ul><ul><li>Amount of K 2 CO 3 =1382/138.21=10.00 mol </li></ul><ul><li>Mass of water=10.00/0.250=40.0 kg </li></ul>
13. 13. Mass percent (%w/w) = mass of solute = ---------------------------------------------- x 100% mass of solute + mass of solvent
14. 14. A sample problem <ul><li>What is mass percent of magnesium sulfate in solution containing 43.5 g of solute in 0.348 kg of solution? </li></ul><ul><li>Mass of solution=348 g </li></ul><ul><li>%w/w MgSO 4 =(43.5/348) x 100%=12.5% </li></ul>
15. 15. Another sample problem <ul><li>What is the mass of manganese (II) chloride in 640. lb of its 30.0% solution? </li></ul><ul><li>Mass of MnCl 2 =(640x30)/100=192 lb </li></ul>
16. 16. Another sample problem <ul><li>What is the mass of 45% solution containing 9.00 kg of potassium iodide? </li></ul><ul><li>Mass of solution=(9.00/45%)x100%=20.0kg </li></ul>
17. 17. Volume percent (%v/v) = volume of solute = -------------------------- x 100% volume of solution
18. 18. Mole fraction (X) = amount (mol) of solute --------------------------------------------------------- amount (mol) of solute + amount (mol) of solvent
19. 19. Mole percent (mol %) = mole fraction x 100%
20. 20. A sample problem <ul><li>What is the mole fraction and mole percent of 157.55g of nitric acid in mixture with 900.8 ml of water? </li></ul><ul><li>Amount of HNO 3 =157.55/63.018 = 2.5000 mol </li></ul><ul><li>Amount of H 2 O=900.8/18.016=50.00 mol </li></ul><ul><li>Total amount = 2.5000+50.00=52.50 mol </li></ul><ul><li>X HNO 3 =2.5000/52.50=0.04762 </li></ul><ul><li>mol % HNO 3 = 0.04762 x 100%=4.762% </li></ul>
21. 21. A sample problem on expressing concentration in parts by mass, parts by volume, and mole fraction.
22. 22. A sample problem on converting concentration units.
23. 23. THE END
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