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Aqueous Solutions and Concentration

Aqueous Solutions and Concentration. A. Definitions. Solution - homogeneous mixture. Solute - substance being dissolved. Solvent - present in greater amount. A. Definitions. Solute - KMnO 4. Solvent - H 2 O. B. Solvation. Solvation – the process of dissolving.

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Aqueous Solutions and Concentration

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  1. Aqueous Solutions and Concentration

  2. A. Definitions • Solution - homogeneous mixture Solute - substance being dissolved Solvent - present in greater amount

  3. A. Definitions Solute - KMnO4 Solvent - H2O

  4. B. Solvation • Solvation – the process of dissolving solute particles are surrounded by solvent particles First... solute particles are separated and pulled into solution Then...

  5. - + - - + + acetic acid salt sugar B. Solvation Non- Electrolyte Weak Electrolyte Strong Electrolyte solute exists as ions and molecules solute exists as ions only solute exists as molecules only DISSOCIATION IONIZATION View animation online.

  6. B. Solvation • Dissociation • separation of an ionic solid into aqueous ions NaCl(s)  Na+(aq) + Cl–(aq)

  7. B. Solvation • Ionization • breaking apart of some polar molecules into aqueous ions HNO3(aq) + H2O(l)  H3O+(aq) + NO3–(aq)

  8. B. Solvation • Molecular Solvation • molecules stay intact C6H12O6(s)  C6H12O6(aq)

  9. NONPOLAR NONPOLAR POLAR POLAR B. Solvation “Like Dissolves Like”

  10. B. Solvation • Soap/Detergent • polar “head” with long nonpolar “tail” • dissolves nonpolar grease in polar water

  11. A. Concentration • The amount of solute in a solution. • Describing Concentration • % by mass - medicated creams • % by volume - rubbing alcohol • ppm, ppb - water contaminants • molarity - used by chemists • molality - used by chemists

  12. mass of solvent only 1 kg water = 1 L water B. Molality

  13. B. Molality • How many grams of NaCl are req’d to make a 1.54m solution using 0.500 kg of water? 0.500 kg water 1.54 mol NaCl 1 kg water 58.44 g NaCl 1 mol NaCl = 45.0 g NaCl

  14. B. Molality • Find the molality of a solution containing 75 g of MgCl2 in 250 mL of water. 75 g MgCl2 1 mol MgCl2 95.21 g MgCl2 0.25 kg water = 3.2m MgCl2

  15. C. Dilution • Preparation of a desired solution by adding water to a concentrate. • Moles of solute remain the same.

  16. C. Dilution • What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution? GIVEN: M1 = 15.8M V1 = ? M2 = 6.0M V2 = 250 mL WORK: M1 V1 = M2 V2 (15.8M)V1 = (6.0M)(250mL) V1 = 95 mL of 15.8M HNO3

  17. D. Molarity • Molarity is the most important unit of concentration. • Molarity = moles of solute liters of solution Symbol for Molarity is M.

  18. Example: A solution contains 23 g of NH4Cl per 145 mL solution. What is its molarity?

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