Solutions Pre-AP

1. Solutions Pre-AP

2. Chapter 13: Solutions

3. Chapter 13.1: Types of Mixtures • Suspensions • Particles in a solvent are so large that they settle out • Can be separated by filtration

4. Colloids • Particles are small enough to stay suspended in solution by the constant movement of surrounding molecules. • Detecting a colloid • Tyndall effect - colloids scatter light.

5. Solutions

6. Solution • Solute-the part that gets dissolved • Solvent-the part that does the dissolving

7. Practice: • Identify the solute and solvent in the following solutions: • 10.0 g of sugar & 40.0 g of water solute: ____________solvent: ___________ b) 75 g of KBr & 100 g water solute: ____________solvent: ___________

8. Liquid Solvents and Solutes • Miscible: liquids that dissolve freely in one another in any proportion • Immiscible: liquids that are not soluble in one another

9. Temperature Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.

10. Temperature • The opposite is true of gases. Higher temperature drives gases out of solution. • Carbonated soft drinks are more “bubbly” if stored in the refrigerator. • Warm lakes have less O2 dissolved in them than cool lakes.

11. Saturation

12. Chapter 13.2: The Solution Process • Solubility • For every combination of solvent with a solid solute at a given temperature, there is a limit to the amount of solute that can be dissolved • Solution equilibrium is the physical state in which dissolution and crystallization of a solute occur at equal rates. • Dissolution • the process of dissolving a solid substance into a solvent to make a solution • Crystallization • process of formation of solid crystals precipitating from a solution

13. Solution Definitions • Soluble - capable of being dissolved • 2. Solution – homogeneous mixtures • 3. Saturated – exactly the right amount of dissolved solute for a particular solvent • 4. Unsaturated –less solute than can be dissolved by a solvent to be saturated • 5. Supersaturated -more dissolved solute than saturated. Has to be specially made; unstable

14. Supersaturated Supersaturated solutions are unstable, and usually accomplished in one of two ways: • Warm the solvent so that it will dissolve more, then cool the solution • Evaporate some of the solvent carefully so that the solute does not solidify and come out of solution.

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

16. Supersaturation • http://www.youtube.com/watch?v=HnSg2cl09PI • http://www.youtube.com/watch?v=nvHrXr5Jajg&feature=related

17. Decide whether each of the following is:U: unsaturated (under line)S: saturated (on line)SS: supersaturated (above line) Solubility Curves a) 50 g KCl in 100 g of water at 90°C. ____ b) 50 g KCl in 100 g of water at 60°C. ____ c) 100 g KNO3 in 100 g of water at 60°C. ____

18. Solubility Curves • Name the solutes that are supersaturated at 60°C, when 140 grams od solute is dissolved in 300 grams of water. • Name the solutes that are saturated at the same conditions. • Name the solutes that are unsaturated at the same conditions.

19. Molarity

20. moles solute ( M ) = Molarity liters of solution Concentration of Solute The amount of solute in a solution is given by its concentration.

21. So therefore… M (molarity) = moles (solute) Liters (solvent) And… M (molarity) = _____grams (solute) ____________ Molar Mass (solute) * Liters (solvent) Grams solute = MM * Liters * M (molarity)

22. PROBLEM: Dissolve 5.00 g of NiCl2•6 H2O in enough water to make 250 mL of solution. Calculate the Molarity. Step 1: Calculate moles of NiCl2•6H2O Step 2: Calculate Molarity [NiCl2•6 H2O ] = 0.0841 M

23. USING MOLARITY What mass of oxalic acid, H2C2O4, is required to make 250. mL of a 0.0500 M solution? Step 1: Change mL to L. 250 mL * 1L/1000mL = 0.250 L Step 2: Calculate. Moles = (0.0500 mol/L) (0.250 L) = 0.0125 moles Step 3: Convert moles to grams. (0.0125 mol)(90.00 g/mol) = 1.13 g moles = M•V

24. Density • Density = grams/mL • Density of Water is 1 • So 500mL of H20 has a mass of 500g

25. mol solute m of solution = kilograms solvent Two Other Concentration Units MOLALITY, m % by mass grams solute *100 grams solution % by mass= mass solution = mass solute + mass solvent

26. Calculating Concentrations Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H2O. Calculate molality and % by mass of ethylene glycol.

27. Calculating Concentrations Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H2O. Calculate m and % of ethylene glycol (by mass). Calculate molality Calculate weight %

28. Warm-Up • You are given three samples of liquid and asked to determine the types of mixture. You are pretty sure that there is one solution, one colloid, and one suspension. Write two paragraphs describing how you are going to determine which sample is each type of mixture.

29. Water The three phases of water are visible from space

30. Structure of Water • In a water molecule two hydrogen atoms form bonds with one oxygen atom. • Because oxygen is more electronegative, the region around oxygen has a partial negative charge. • The region near the two hydrogen atoms has a partial positive charge. • A water molecule is a polar molecule with opposite ends of the molecule with opposite charges.

31. Structure of Water http://www.shorstmeyer.com/jpgs/watermolec.jpg

32. Hydrogen Bonding • Water molecules are attracted to each other. • The attraction is electrical. • The negative region near the oxygen atom is attracted to the positive region near a hydrogen atom creating a hydrogen bond.

33. Hydrogen Bonding • The hydrogen bonds between molecules of water results in some of waters most important properties. • High Cohesion • High Adhesion • High Specific Heat • Expands Upon Freezing • Dissolves Many Substances

34. Cohesion • Attraction between molecules of the same substance. • The prefix co- means “common” • Hesion means “to stick” • So cohesion means “an attraction” or “sticking” between molecules that have properties “in common” • Causes liquid droplets to take on a spherical shape

35. Cohesion among water molecules plays a key role in the transport of water against gravity in plants. • Water that evaporates from a leaf is replaced by water from vessels in the leaf. • Hydrogen bonds cause water molecules leaving the veins to tug on molecules further down. • This upward pull is transmitted to the roots. Fig. 3.2

36. Surface tension, a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion. • Water has a greater surface tension than most other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface. • Water behaves as if covered by an invisible film. • Some animals can stand, walk, or run on water without breaking the surface.

38. Adhesion • Attraction between molecules of different substances. • Creates the meniscus in a graduated cylinder • The prefix ad- means “toward” so adhesion is the “attraction” of one substance “toward” another

39. Expands on Freezing

40. Dilutions

41. The Dilution formula M1V1 = M2V2 Molarity 1 * Volume 1 = Molarity 2 * Volume 2 Ex. If we have 1 L of 3 M HCl, what is M if we dilute the acid to 6 L? M1 = 3 mol/L V1 = 1 L V2 = 6 L M1V1/V2 = M2 M2 = (3 mol/L x 1 L) / (6 L) = 0.5 M

42. Practice problems Q – What volume of 0.5 M HCl can be prepared from 1 L of 12 M HCl? M1V1/M2 = V2 M1 = 12 mol/L V1 = 1 L M2 = 0.5 L V2 = (12 mol/L x 1 L) / (0.5 L) = 24 L

43. Warm-Up • Complete the reaction and determine the precipitate. Be(ClO4)2 + KOH 

44. Factors Affecting Solubility

45. 3 Factors that increase rate of Dissolving for solids in a liquid solution 1. Surface area - Increase of surface area increases rate of dissolving. Increase surface area by breaking/grinding solid 2. Agitation – Shaking/stirring a solution will increase the rate of dissolving 3. Heat- increase in temperature usually increases the rate of dissolving

46. 2 factors that increase the rate of dissolving for a gas in a liquid 1. Temperature- increase in temperature usually decreases the rate of dissolving 2. Pressure- Increase in pressure increases the rate of dissolving. ***Pressure has little/no effect on the dissolving rate of a solid in a liquid***

47. Factors Affecting Solubility • 1. Types of solvents and solutes • a. “Like dissolves like” • A polar solvent, such as water, will dissolve polar and ionic solutes. Nonpolar solvents, such as oils, will dissolve other nonpolar solutes. • 2. Pressure • a. Liquids and solids little to no effect • b. Gases - solubility increase with increased pressure • c. Henry’s law - solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid Ex: carbonated beverages. • 3. Temperature • Liquids and solids - increase temperature increase solubility (mostly) • b. Gases - increase temperature decrease solubility

48. Solid vs. Gas Solid Solutes Gas Solutes

49. Electrolytes

50. Some solutions conduct electricity, some don’t Electrolytes – compounds that conduct an electric current in an aqueous solution OR in the molten state. An electrolyte solution contains charged particles (ions), which can move. Any salt dissolved in water is an electrolyte: NaCl, KI, etc.