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solutions

< 1 nm. > 100 nm. solutions. colloids. suspensions. transparent (clear). transparent with Tyndall effect (scattering of light). translucent (cloudy). molecular motion. movement by gravity. coagulation – can settle. never settle. < 1 nm. > 100 nm. solutions. colloids. suspensions.

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solutions

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  1. < 1 nm > 100 nm solutions colloids suspensions transparent (clear) transparent with Tyndall effect (scattering of light) translucent (cloudy) molecular motion movement by gravity coagulation – can settle never settle

  2. < 1 nm > 100 nm solutions colloids suspensions Tyndall Effect? Scattering in all directions Absorption of light Passage of light Scattering in beam

  3. Does a chemical reaction take place when one substance dissolves in another? No, dissolving is a physical change because no new substances are formed. When one substance dissolves in another, the resulting mixture is called a solution.

  4. Solutions

  5. Does a chemical reaction take place when one substance dissolves in another? No, dissolving is a physical change because no new substances are formed. Whenone substance dissolves in another, the resulting mixture is called a solution.

  6. Some Definitions HOMOGENEOUS A solution is a _______________mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENTand the others as SOLUTES.

  7. Parts of a Solution Solute Solvent • Thesubstance that is dissolved • The substance present in a smaller amount • The substance that dissolves the solute • Thesubstance that is present in the greater amount • Thesolvent determines the state of the solution Solute + Solvent = Solution

  8. “Like dissolves like” • Polar dissolves in polar and ionic Ex. Sugar and Water • Non-polar dissolves in non-polar Ex. oil and soap

  9. The solute breaks up into tiny particles that spread evenly throughout the solvent. In a solution of sugar water, sugar is the solute, and water is the solvent.

  10. Are all solutions liquids? • No! Many types of solutions are possible. Let’s talk about a few examples.

  11. Alloy- a mixture done by the melting of two or more metals

  12. How do I get solutes to dissolve faster in solvents? Ex. Sugar in iced tea? Stir, and stir, and stir Fresh solvent contact and interaction with solute Add temperature Faster rate of dissolution at higher temperature Grind the solute to make it smaller Greater surface area, more solute-solvent interaction

  13. SOLUBILITY • Definition: The maximum amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure. • Soluble- the solute can be completely dissolved in the solvent • Insoluble- the solute cannot be dissolved in the solvent. In fact, it separates completely.

  14. When two liquids totally mix they are said to be miscible. When two liquids do not mix they are said to be immiscible. Miscible vs. Immiscible

  15. Na+ Cl- Dissolving process in water When particles of the solute are completely dispersed and surrounded by particles of the solvent, this process is called SOLVATION.

  16. Na+ Cl- The separation of the ions in an ionic compound (usually by dissolving water) is called DISSOCIATION For water: POLAR-POLAR For hydrated ion: Ion-polar For NaCl (s): ion-ion

  17. IONIZATION • The physical process of converting an atom or a compound into ions by adding or removing electrons. Usually done by a solvent in a solution.

  18. Definitions Solutions can be classified as saturated or unsaturated. A saturated solution-Contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution-Containsless than the maximum amount of solute that can dissolve at a particular temperature

  19. Definitions SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved Supersaturated solutions are unstable. The supersaturation is only temporary, and usually accomplished in one of two ways: • Warm the solvent then cool the solution • Evaporate some of the solvent. http://www.youtube.com/watch?v=XSGvy2FPfCw

  20. Supersaturated Sodium Acetate • One application of a supersaturated solution is the sodium acetate “heat pack.”

  21. Aqueous Solutions (water is the solvent) How do we know ions are present in aqueous solutions? If the solution conducts electricity it is called an ELECTROLYTE

  22. Types of solutes high conductivity Strong Electrolyte - 100% dissociation, all ions in solution Na+ Cl-

  23. Types of solutes slight conductivity Weak Electrolyte - partial dissociation, molecules and ions in solution CH3COOH CH3COO- H+

  24. Aqueous Solutions Some compounds dissolve in water but do not conduct electricity. They are called NONELECTROLYTES. Examples include: sugar ethanol ethylene glycol

  25. Types of solutes no conductivity Non-electrolyte - No dissociation, all molecules in solution sugar

  26. Electrolytes in the Body • Carry messages to and from the brain as electrical signals • Maintain cellular function with the correct concentrations electrolytes

  27. Concentration • The measure of how much solute is dissolved in a specific amount of solvent or solution. • Concentrated large amount of solute high Molarity • Diluted small amount of solute low Molarity

  28. Percent by Mass • The ratio of the solute’s mass to the solution’s mass expressed as a percent. Percent by Mass = mass of solute mass of solution X 100

  29. Calculating Percent by mass • What is the percent by mass of NaHCO3 in a solution containing 20 g NaHCO3 dissolved in 600 ml of H2O? % mass NaHCO3 % mass = mass solute mass solution 20 g NaHCO3  solute 600 ml H2O  solvent 1 ml H2O = 1 g H2O  600 g H2O Unknown Formula X 100 Given Implied % mass = 20g NaHCO3 620 g H2O X 100 = 3%

  30. Your turn • You have been given 3.6 g NaCl that you then dissolve in 525 g of water. What would be the percentage by mass of NaCl?

  31. moles solute ( M ) = Molarity liters of solution Molarity • The number of moles of solute dissolved in per liter of a solution. Molarity = moles of solute = mol liters of solution L

  32. Calculating Molarity • What is the molarity of an aqueous solution containing 40.0 g of glucose (C6H12O6) in a 1500 ml solution? • If given 340 g of CuCl2, what would be the molarity of the solution if it was dissolved in 6425 cm3 of water? Note: (1 cm3 = 1 ml)

  33. mol solute Molality (m) = kilograms solvent molality • Since the volume of a solution changes as temperature changes, the Molarity of the solution changes as well. Therefore, sometimes it is more useful to use molality. Note 1 Kg= 1000 g • Why? Because masses do not change with temperature!

  34. Calculating molality • What is the molality of a solution containing 10.0 g Na2SO4 dissolved in 1000.0 g of water? • What is the molality of a solution containing 30.0 g of naphthalene (C10H8) dissolved in 500.0 g of toluene?

  35. Practice Problems • Calculate the percent by mass of 3.55 g NaCl dissolved in 88 g water. • Calculate the percent by mass of benzene in a solution containing 14.2 g of benzene in 28.0 g of carbon tetrachloride. • What is the molarity of the following solutions? • 15.25 g MgCl2 in 500 mL of solution • 2.48 g CaF2 in 375 cm3 of solution • Calculate the molality of the following solutions: • 20.0 g CaCl2 in 700.0 g H2O • 3.76 g NaOH in 0.850 L H2O

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