1. Colligative Properties

2. Can a solute change the properties of a solvent when added together to create a solution?

3. consider aqueous solutions solvent = water How do properties of aqueous solution compare to properties of pure water?

4. Conductivity pure water does not conduct electricitypure water does not conduct electricity –some aqueous solutions do to conduct electricity a solution must contain ionsto conduct electricity a solution must contain ions

5. conductivity depends on nature of the solute particles

6. molecular (covalent) solutes DO NOT conduct in any form C 6 H 12 O 6(s)C 6 H 12 O 6(s) C 6 H 12 O 6(aq)C 6 H 12 O 6(aq)

7. ionic solutes DO conduct in aqueous and liquid forms but NOT in solid form NaCl(s)NaCl(s) NaCl(l) √NaCl(l) √ NaCl(aq) √NaCl(aq) √

8. Colligative Properties depend on number particles in solution NOT type particles –doesn’t matter what kind of particles (ions or molecules) does –concentration of particles does matter

9. What are some colligative properties? vapor pressure (VP)vapor pressure (VP) –decreases (↓) freezing point (fp)freezing point (fp) –decreases (↓) boiling point (bp)boiling point (bp) –increases ( ↑) change in Osmotic Pressurechange in Osmotic Pressure

10. higher the concentration of solute particles, the greater (larger) the effect on colligative properties

11. Does it matter if solute is ionic or covalent? YES number of particles will vary –effected by concentration: greater concen = greater effect lower concen = lesser effect

12. ionic solutes dissolve in H 2 O dissociate into (+) & (-) ions [  more particles/moles solute]

13. MgCl 2 (s) + H 2 O(l)  Mg 2+ (aq) + 2Cl(aq) MgCl 2 (s) + H 2 O(l)  Mg 2+ (aq) + 2Cl(aq) 1 mole salt  3 moles ions 1 mole salt  3 moles ions (MgCl 2 ) (Mg +2 & 2Cl -1 ) (MgCl 2 ) (Mg +2 & 2Cl -1 ) NaCl(s) + H 2 O(l)  Na +1 (aq) + Cl -1 (aq) NaCl(s) + H 2 O(l)  Na +1 (aq) + Cl -1 (aq) 1 mole salt  2 moles ions 1 mole salt  2 moles ions (NaCl) (Na +1 & Cl -1 ) (NaCl) (Na +1 & Cl -1 )

14. Covalent solutes dissolve as molecules dissolve as molecules  1-to-1 relationship between moles solute & moles dissolved particles

15. Covalent substances C 6 H 12 O 6 (s) + H 2 O(l)  C 6 H 12 O 6 (aq) C 6 H 12 O 6 (s) + H 2 O(l)  C 6 H 12 O 6 (aq) 1 mole sugar → 1 mole dissolved molecules 1 mole sugar → 1 mole dissolved molecules C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq) C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq)

16. As solute is added to a solvent, what happens to freezing point & boiling point of solution? 1)The freezing point ↓ & the boiling point ↓ 2)The freezing point ↓ & the boiling point ↑ 3)The freezing point ↑ & the boiling point ↓ 4)The freezing point ↑ & the boiling point ↑ Answer: 2

17. Which solution containing 1 mole of solute dissolved in 1000 g of water has the lowest freezing point? 1)C 2 H 5 OH(aq) 2)NaCl(aq) 3)KOH 4)CaCl 2 Be careful! - do you want greatest or least change? What if question asked which solution has highest freezing point? Answer: 4

18. Of the following solutions, the one that will freeze at the lowest temperature contains 1 mole of nonvolatile solute dissolved in 1) 250 g of solvent 2) 500 g of solvent 3) 750 g of solvent 4) 1000 g of solvent Answer: 1

19. Which solute, when added to 1000 g of water, will produce a solution with the highest boiling point? 1) 29 g of NaCl 2) 58 g of NaCl 3) 31 g of C 2 H 6 O 2 4) 62 g of C 2 H 6 O 2 58g (1 mole) of NaCl → 2 moles of ions 2 moles of ions 62g (1 mole) of C 2 H 6 O 2 → 1 mole of molecules 1 mole of molecules

20. Which solution will freeze at the lowest temperature? 1) 1 g of NaCl dissolved per 100 g of H 2 O 2) 1 g of NaCl dissolved per 1000 g of H 2 O 3)1 g of C 12 H 22 O 11 dissolved per 100 g of H 2 O 4) 1 g of C 12 H 22 O 11 dissolved per 1000 g of H 2 O

21. Which solution will freeze at the lowest temperature? 1) 1 g of NaCl dissolved per 100 g of H 2 O __1 g___ = 0.0043 mol of molecules __1 g___ = 0.0043 mol of molecules 232 g mol 232 g mol 2) 1 g of C 12 H 22 O 11 dissolved per 100 g of H 2 O __1 g____ = 0.017 mol → 0.034 mol of ions 58.8 g/mol (NaCl) (Na +1 and Cl -1 )

22. Effect of Non-volatileSolute on Colligative properties: Effect of Non-volatile Solute on Colligative properties: Boiling Point Elevation ( ↑ )Boiling Point Elevation ( ↑ ) Freezing Point Depression (↓)Freezing Point Depression (↓) the more particles, the bigger the effect!the more particles, the bigger the effect! –the higher the bp and the lower the fp

23. Applications of colligative properties: 1. salting roads in the winter time ? NaCl or ? CaCl 2 2. using salted ice to make ice cream - keeps ice cream from becoming like concrete