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Welcome to Chem 121-01 è HAPPY NEW YEAR !!! è Pick up CAPA #1 - outside on shelf è Pick up syllabus - in front è Get your photo taken - get index card.

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Presentation on theme: "Welcome to Chem 121-01 è HAPPY NEW YEAR !!! è Pick up CAPA #1 - outside on shelf è Pick up syllabus - in front è Get your photo taken - get index card."— Presentation transcript:

1 Welcome to Chem è HAPPY NEW YEAR !!! è Pick up CAPA #1 - outside on shelf è Pick up syllabus - in front è Get your photo taken - get index card

2 Outline:1/10/07 n n Go over course syllabus What to expect? n Plus ça change: n Plus la même chose:  ACS standardized final (cumulative over two semesters)  CAPA, keypads, text & lectures…

3 Outline:1/10/07 n n Any questions? Do DISCUS post assignment… Read Chapter 12…try CAPA early…

4 Outline:1/10/07 n n Any questions? n n Start chapter 12 - Solutions Solution properties Colligative properties

5 Some Aqueous Properties: n n Solution: n n Solvent: n n Solute: n n Aqueous Solution: n Homogenous mixture of 2 or more components n Majority component of solution n Minority component of solution n Solvent is H 2 O, denoted as species (aq)

6 Types of solutions: Table 12-1 (p.484)

7 More Definitions A solution holding the maximum solute is...saturated A solution holding the maximum solute is...saturated A solution that can hold more solute is...unsaturated A solution that can hold more solute is...unsaturated A solution that is holding too much solute is...supersaturated A solution that is holding too much solute is...supersaturated

8 Supersaturated Sodium Acetate A supersaturated solution of NaCH 3 COO. 3H 2 O is made by dissolving a large amount of the solid into a few mL of water on a hot plate

9 Supersaturated Sodium Acetate A seed crystal is added to the flask…

10 Supersaturated Sodium Acetate Upon hitting the solution, it supplies a template for the solute to follow

11 Supersaturated Sodium Acetate Five pieces must come together in just the right pattern… Na + CH 3 COO  3 H 2 O NaCH 3 COO 3H 2 O(s) Sodium acetate trihydrate

12 Supersaturated Sodium Acetate The solution rapidly crystallizes outward from the seed locations

13 Supersaturated Sodium Acetate

14 In going from a “liquid” state to a solid state, the  H fus is released as heat!

15 Supersaturated Sodium Acetate To redissolve the solid, put the  H fus back in…

16 Concentrations of solutions: Molarity: Molality: Mole fraction: ppm, ppb: Mols solute / L solvent Mols solute / kg solvent Mols solute / mols total Part per million/billion…

17 Molarity: (unit of concentration) n n Definition: Mols/Liter (M) Example: 4.0 g of NaOH dissolves into 1L What is the molarity of the solution? n Convert to moles n Calculate moles/liter 4.0g  1 mol/40g = 0.1 mol 0.1 mol/L = 0.10 M

18 Molarity Problems: n Instead of “grams of sample”… given: molarity of aqueous sample! n You must also be given the volume… X Why? n No converting grams into moles… multiply Molarity  volume = moles

19 Molarity Examples: n Given: mL of M NaOH How many moles of NaOH? u Units analysis: L × mol/L = 2.760e -3 mol Practice!!!

20 Molality Examples: n n 20.0 g of zinc(II) chloride is dissolved in a 250 mL volumetric flask, and water is added to the mark. n n Calculate the molality of chloride anions What to do first?

21 n Translate words & write equations:  ZnCl 2 (s) → Zn 2+ (aq) + 2Cl  (aq) n Convert grams into moles: Molar mass (ZnCl 2 ) = g/mol 20.0g / g/mol = mol ZnCl 2 n Divide moles into kg of solvent: mol / kg = m ZnCl 2

22 What is the molality of Cl  ions? m  2 mol Cl  (aq) /1 mol ZnCl 2 ZnCl 2 = 1.18 m Cl  Must be able to work both directions: What mass of NaCl is needed to make a 100 mL solution of 0.50 M NaCl? = 2.92 g NaCl

23 Aqueous Properties: Like dissolves like…. Polar species dissolve in polar solvents Non-polar species dissolve in non-polar solvents e.g. Which of the following would most likely dissolve in benzene? (A) H 2 O (B) CH 3 COOH (C) C 3 H 8 (D) C 6 H 5 NH 2 (A) H 2 O (B) CH 3 COOH (C) C 3 H 8 (D) C 6 H 5 NH 2

24 Hydrophobic Hydrophilic Other definitions: Water-fearing Water-loving

25 Hydrophobic p.108

26 Hydrophobic Hydrophilic Biochemical terms (p.510) Monolayer Micelle Vesicle Other definitions:

27 Like dissolves like…. p.108

28 Surfactants: n n Anything which alters behavior of solute-solvent mixture….(e.g. soap) Applications? NaCl in cooking Road salt for ice Antifreeze Saline drips Gatorade


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