Solubility of Solids & Gases Chapter 18 PART 1

1. Solubility of Solids & Gases Chapter 18 PART 1 Note to self: put in video!

2. NaCl.dissolving.mov So what do you mean “dissolve”?? Solubility- the max amt of a subst that will dissolve in a certain quant of water, at a specific temp Ex: sol. of KNO3 is 60g at 40C If I heat up the water, will that help me dissolve more solute?

3. Remember: Solute- what you are dissolving (what you have less of) Solvation-process that occurs when ionic process dissolves SOLUTE Solvent- what you are dissolving the solute in. Ex: water (what you have more of) SOLVENT Solution- homogeneous mixture of 2 or more subst. (the solUTE + solVENT!)

4. So…”If I stir more, will that help me dissolve more?” Based on the graph? NO! Makes it dissolve faster, but not more of it.

5. Solubility vs. Temperature • What term describes 39g NaCl at 70C? • Saturated! • What about 30g at same T? • Unsat! • What about 45g at same T? • SUPERsat!

6. = PART (* 100!) WHOLE Solution Concentration • Does everything fit into those 3 vocab terms? • What about %? (Parts per 100) • in here…

7. Ex – what would % be of 5 grams of salt added to 95 g of water? Part = Whole 5 5+95 = 5 100 = 5%! • But is 0.005% really helpful? • So… also have ppm & ppb (million/billion) DEMO!

8. Dissolving Ionic Compounds • From a MACROscopic perspective, we say salt is dissolved in water when we can’t see it any longer. But is that what is REALLY happening SUBmicroscopically? • Water is POLAR.What does that make you think of? • Polar bear maybe? North/south pole? • Need to think like the earth’s poles – they are OPPOSITE each other

9. - - - - - + + POLAR??? • Polar basically means that the electrons that make up the molecule (water) are NOT spread out evenly.

10.  if more negative stuff is on 1 side, then that side will be PARTIALLY negative. • Which side will be more negative: H or O? • Explain! • Whole molc is still neutral!!

11. SO what?? • So.. If a molc has a slight + charge to it, what will it be attracted to? • What could that have to do with dissolving?? • What is table salt again?? • What is the charge of each ion involved?

12. What does each color represent? Which side of the water will be attracted to the green chlorine ion? Will just one slightly + ion be able to pull the Cl- away from the Na+? What about a bunch of them?

13. Crystal structure of NaCl “Aqueous Salt” (not liquid!) Explain this diagram. What is this showing? NaCl.dissolving.mov • NaCl.Aqueous.Soln.mov • Look how ionic compounds dissolve! SugarH2O_dissolve.mov Why doesn’t it break up too?

14. So based on those pics & concepts, when will water be able to dissolve something? • What if the charges btw the ionic cpd are too high for water to pull them away from each other? “INSOLUBLE”

16. WS Solubility Practice a curvy subject

17. Crystal structure of NaCl “Aqueous Salt” (not liquid!) Explain this diagram. What is this showing? NaCl.dissolving.mov • NaCl.Aqueous.Soln.mov • Look how ionic compounds dissolve! SugarH2O_dissolve.mov Why doesn’t it break up too?

18. So based on those pics & concepts, when will water be able to dissolve something? • What if the charges btw the ionic cpd are too high for water to pull them away from each other? “INSOLUBLE”

19. Effects of Dissolving Compounds in WaterPART 2 Rate of Dissolving Colligative and Electrolytic Properties

20. What if you are impatient?How can we speed up the dissolving process? • Well, what is causing it to dissolve? • Interactions btw solvent & solute particles. • So how to get more collisions? • STIR • HEAT • Increase SURFACE AREA • Explain…

21. Na+ Cl- C12H22O11 Colligative Properties 1. Freezing Point Depression • The more particles present, the colder it will have to be for the solid to form. • There are twice as many solute particles in the salt solution, so the effect of salt on fp is about twice the effect of sugar.

22. Colligative properties 2. Boiling point elevation • The more particles present, the hotter it will have to be for the gas to form.

23. Which has a greater effect on the bp? 1.0 M NaOH 5.0 M NaOH (five times as concentrated) The more solute present, the higher the boiling point. bp = 100.512 oC bp = 102.56 oC

24. - - - + + + + - - Difference btwn dissolving Ionic & Covalent compounds. • Ionic cpds – made of ions! • Metal ion + nonmetal ion (L & R of per tbl) • Ex: NaCl • Forms electrolytes • Molecular cpds – made of molecules • Nonmetal + nonmetal (both R side of per tbl) • Ex: H2O, CO2 • Non-electrolytes This is important stuff!!!!

25. - - + • Water separates ionic compound into all of its IONS • When ionic compounds ionize the solution becomes an electrolyte • Electrolytes conduct electricity 3 PARTICLES FORM

26. - - + - - + Ionization • Water separates ionic compound into all of its IONS • BaCl2 Ba+ + 2Cl- 3 PARTICLES FORM

27. + + + + + + + + - - - - COVALENT Compounds Dissolve separating MOLECULES • Water separates molecules from each other, but doesn’t break up molecule 1 PARTICLE FORMs

28. 1.0 M KCl 1.0 M Mg(NO3)2 Predict the effect on bp of using different solutes of equal molarity. bp=101.024 oC bp = 101.536 oC

29. Which of the following would cause the greatest change in colligative properties if the same amount of each were added? • C6H12O6 (Sugar)-Molecular • NaCl (Table salt)-Ionic • CaCl2- Ionic

30. = 1 particle • covalent bonds only • does not dissociate • non-electrolyte • C6H12O6 (Sugar) • NaCl (Table salt) • CaCl2 = 2 particles • dissociates into a Na+ & Cl- • electrolyte = 3 particles • dissociates into Ca+ & 2Cl- • electrolyte • Greatest Change in Colligative Prop

31. Boiling point goes UP Once this stuff is in the water, what effect can it have? When molecules or ions disturb the way the water molecules are arranged, some of the properties of water are changed! The more particles there are, the greater the effect. So that means water could boil at _______ & freeze at ___________ when solutes are added. 105 C -5 C Freezing point goes DOWN

32. SUMMARY! • Polar solvents will dissolve… • Polar solutes AND • Ionic solutes • Nonpolar solvents will dissolve… • NONPOLAR solutes • Like Dissolves Like! • Why might water be called the “universal solvent?”

33. SUMMARY! • Ionic compounds ionize to form electrolytes • Covalent compounds remain as molecules and generally DO NOT conduct electricity • Acids and Bases are always electrolytes • HCl • H2SO4 • NaOH • HC2H3O2

34. Gas Solutions PART 3

35. cold warm C.9 Dissolved Oxygen Levels • How does gas solubility differ from solids? • What is the solubility of O2 gas in 20C? 40C? • As T , solubiliy  • Note diff in units – mg vs g – much less will dissolve!

36. Pressure also affects gas solubility • What is happening in this pic? • Gas is escaping! WHY? • How does Pressure make it more soluble? • So talk about how to make sure your coke doesn’t go flat! What happens if P doubles?

37. Quick question…. One 40 L aquarium is kept at 25C, while a second, identical one is kept at 20C. Which aquarium can support a larger population of fish? WHY? A tank kept at a lower temp will contain more DO!

38. C.10 Temp, DO & LIFE! • Reminder – fish are cold blooded…so? •  T =  metabolism – eat more, swim more, req more DO • Also, the hotter it is, more stuff grows, requiring more DO • Can also have a supersat sol of DO • The “bends” if diving for us • “gas bubble trauma” for fish

39. Why would there be such a difference between summer & winter needs? Do you expect all fish to have the same requirements?