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Solutions

Solutions. Chem 12, 2011. Solutions – What to expect. Basics Terminology Rules Concentration calculations % by mass, % by volume ppm, ppb molarity Theory Solubility curves Practical Preparing solutions Dilutions. Solutions – What are they.

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Solutions

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  1. Solutions Chem 12, 2011

  2. Solutions – What to expect Basics Terminology Rules Concentration calculations % by mass, % by volume ppm, ppb molarity Theory Solubility curves Practical Preparing solutions Dilutions

  3. Solutions – What are they Definition – one compound (solute) dissolved in another (solvent) Classic example is solid/liquid dissolved in water, but any combination is possible Most of what we will study will be solutions with liquid (water) as a solvent General terms Solute: the compound being dissolved Solvent: the medium in which the solute is dissolved Miscible: solute will dissolve in solvent Immiscible: solute will not dissolve in solvent Miscibility

  4. Solutions – Combinations • Solid in liquid - Sol • Solid in gas – Solid aerosol • Solid in solid – Solid sol • Gas in liquid - Foam • Gas in solid – Solid foam • Gas in gas - Gas • Liquid in liquid - Emulsion • Liquid in solid - Gel • Liquid in gas - Aerosol Kool-aid Clouds C. Chip cookie Shaving Cream Styrofoam Air Chocolate milk Jell-o Hairspray

  5. Dissolution (solvation) Solvation (or dissolution) is the process where the crystal structure of a solute is broken up into individual ions (electrolytes) Electrolytes Electrically conductive Often ionic solutions (produced via the break down of ionic compounds) Strong electrolyte: completely ionizes in solution Weak electrolyte: most does not dissolve Note on solvation: For our purposes, the definition above is most appropriate however the breaking up of the crystal structure does not hold true for all types of solutions

  6. Solvation(con’t) Process When the forces of the solvent overcome the intermolecular forces of the solute, it will dissolve Ex. Water “attacks” juice crystals Factors affecting solvation Polarity (like dissolves like) Polar is miscible in polar (immiscible in non-polar) Conditions: altering T, V, or P can alter a solutes ability to dissolve (alters saturation)

  7. Saturation Unsaturated A solution that contains some or none of the solute in question and thus can dissolve more of the compound into solution Saturated solution contains the max amount of solute any further solute will stay as a solid precipitate Supersaturated more of the solute than usual is dissolved into the solution made possible by altering conditions (T, V, P) video

  8. Concentration Definition The ratio between the amount of solute andsolution Methods Molarity (most common; mol/L) m/m % (ratio of the mass of solute to mass of solution) m/v % (ratio of the volume of solute to volume of solution) ppb, ppm (for much smaller proportions; ratio of solute to solvent

  9. Solubility Curves Over time, scientists have performed experiments to determine the solubility of compounds in water Graph shows the temperature on the x axis and solubility on the y axis (in g/100mL) • Factors affecting solubility • Temperature: supersaturation, boiling etc • Pressure: bubbles, pop • Volume: soup • Ion size, charge

  10. Building a curve • Done through experimental collection of data • Take different amounts of solute and find the temp where they dissolve Data for KNO3

  11. Anything that falls below the line is UNSATURATED • Anything above the line is SUPERSATURATED • Most of the curves point up – meaning? • Some point down. -Why?

  12. Problems • What is the solubility of NaNO3 at 40°C? • At what temperature will 50g of KCl dissolve in 100g of water? • How much will you have to add to make it ppt at 75°C? • If you dissolve 140g KI at 15°C how much will ppt out at 5°C? • You have 10g of ammonium chloride at 80°C? What is the saturation? • Give an example of how to make a super saturated solution of sodium sulfate?

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