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Solutions

Solutions. CPS Chemistry. Definitions. Solutions A homogeneous mixture of two or more substances in a single phase Soluble Capable of being dissolved. Solvent Dissolving medium in a solution What is doing the dissolving Solute Substance dissolved in a solution What is dissolved

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Solutions

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  1. Solutions CPS Chemistry

  2. Definitions • Solutions • A homogeneous mixture of two or more substances in a single phase • Soluble • Capable of being dissolved

  3. Solvent • Dissolving medium in a solution • What is doing the dissolving • Solute • Substance dissolved in a solution • What is dissolved • Example • Sugar in tea – • tea is solvent, sugar solute

  4. Types of Solutions • May exist as gasses, liquids or solids • One component is designated as solvent and one as solute • Chart on pg. 396

  5. Phase • If there are two different types of substances it is a phase change • Water + salt; water and gas • Same phase • Water and apple juice • This is an aqueous solution • Means there is water involved • Alcohol and liquid • Tincture solution • Means there is alcohol involved

  6. Mixtures • 2 or more substances when each retains its properties • Homogeneous • Uniform distribution of particles • 0.01-1nm size particles, can be atoms • Can be physically separated • Ex. Salt water, air • Also called solution

  7. Heterogeneous • Distribution of particles is not uniform • Can be separated by physical means • Particle size 1-1000 nm (nanometer)

  8. Suspensions • When particles in a solvent are so large that they settle out unless stirred constantly • Gravity pulls particles to bottom of container

  9. Particles >1000nm in diameter, 1000 times as large as atoms • Ex. Italian salad dressing, muddy water • Can be separated by passing liquid through a filter

  10. Colloids • Has particles that are intermediate in size and they remain dispersed in the solute • 1-1000nm particle size • Emulsion or foam are specific types • Mayonnaise is an emulsion of egg and oil

  11. The Tyndall effect • Is a sign that it may be a colloid • The particles are not large enough to be seen, but large enough to scatter light • Ex: headlights on a foggy night

  12. Test tube Test tube Light Beam Light Beam No Tyndall Effect, beam of light cannot be seen in solutions Tyndall Effect, beam of light can be seen in suspensions and colloids

  13. Electrolytes vs. Nonelectrolytes • Electrolyte • A substance that dissolves in water to give a solution the ability to conduct electricity • Nonelectrolyte • A substance that when dissolved in water to make a solution that does not conduct electricity

  14. When ionic compounds dissolve, the positive and negative ions separate from each other and are surrounded by water molecules • When the ions are free to move, electricity moves easily

  15. How to Make Solutions • You need to know the: • Solubility –the maximum amount solute can dissolve in a solvent • Rate – how fast the solute dissolves

  16. Factors that affect rate of dissolution • Surface area of the solute • The larger the surface area, the more quickly it dissolves • Agitation of a solution • When you stir or shake the solute particles are dispersed throughout the solvent, and it increase the rate of dissolution

  17. Saturated Solutions • A solution that contains the maximum amount of dissolved solute is saturated • The factors that determine saturation are mass of solvent, mass of solute and the temperature • When a solution contains less than the maximum saturation it is considered unsaturated

  18. Supersaturate • A solution that contains more dissolved solute than a saturated solution contains under the same conditions • But will form crystals when disturbed or cooled

  19. Like dissolves like • The rule for predicting whether one substance will dissolve in another is related to the type of bonding, the polarity of a molecule and the intermolecular forces between the solute and solvent • Things need to be similar for them to dissolve

  20. Solvent Solute = Solution Polar Polar = yes Polar non-polar = no Nonpolar Polar = no Nonpolar Nonpolar = yes

  21. Reminder molecule polarity

  22. More Vocab. • Immiscible • Liquid solutes and solvents that are not soluble in each other • Oil and water • Oil and salt • Miscible • Liquids that dissolve freely in one another in any proportion • Water and food coloring

  23. Back to Temperature- Solubility • Increase temp =increase KE= increase in solubility + increase in rate • Higher temps dissolve faster( Liquids) BUT • Gasses act differently • Increase temp = decrease solubility • Because gasses will leave solution at high temps

  24. Pressure –solubility • There is no difference to solids or liquids, but with an increase in pressure it will increase the solubility of a gas • For example CO2 dissolved in a solution of sucrose and water (soda) will come out of solution when the pressure is decreased (opening the bottle, lets the soda bubble)

  25. Size of the Particle – rate • Because the dissolution occurs only at the surface of the solute, when you crush a substance, • You get a larger surface, so you increase the rate at which it is dissolved

  26. Stirring - rate • When you agitate the solvent, you increase the contact with the surface of the solute • You increase the rate

  27. Amount of Solute -rate • As you increase the amount of solute you want to dissolve • You decrease the solubility and rate

  28. Concentration • A measure of the amount of solute in a given amount of solvent or soulution • MATH IS INVOLVED

  29. Molarity • The number of moles of solute in one liter of solution • Molar mass- as a reminder it is the mass listed on the PTE.. If it is for a compound, you simly add the masses of the atoms of the emperical formula • Ex. H2O H=1.00 O=15.99 total molar mass is 1.00+1.00+15.99 =17.99g

  30. Formula Amount of solute (mol) Molarity ( M) = ______________________ Volume of solution (L)

  31. Practice • You have3.50 L of solution that contains 90.0 g of sodium chloride, NaCl. What is the molarity of that soulution? • Mass of solute 90.0 • Solution volume = 3.50 L • Molar Mass if NaCl 58.44 g/mol

  32. Molality • Don’t confuse them… • The concentration of a solution expressed in moles of solute per kilogram of solvent • You measure the mass of the solvent…

  33. Formula moles of solute (mol) Molality = ______________________ mass of solvent (Kg)

  34. Practice • A solution was prepared by dissolving 17.1 g of sucrose C12H22O11 in 125g of water. Find the molal concentration • Given Solute mass = 17.1g sucrose • Solvent mass = 125 g H2O

  35. Colligative Properties • Boiling- point elevation • Freezing-point depression • Vapor-pressure lowering • Osmotic pressure

  36. These change in relation to the total number of solute particles present • They are a constant that can be used to calculate the changes in solvents that contain nonvolatile solutes • Electrolytes have greater affects on colligative properties

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