Solutions. Making sense of the aqueous world

Transcription

1 Solutions Making sense of the aqueous world :13:55 1/42 Notessolutionsroessler (#2)

2 Solution :13:55 2/42 Notessolutionsroessler (2/42)

3 Solutions They are homogenous Homogenous- Same throughout, can t discern a difference Heterogenous- not the same throughout Solute- the one that is getting dissolved Solvent- The one that is doing the dissolving (water) Aqueous- Water is the dissolving solvent :13:55 3/42 Notessolutionsroessler (3/42)

4 Universal Solvent :13:56 4/42 Notessolutionsroessler (4/42)

5 Quick Review Covalent- Sharing of electrons equally Polar Covalent- Unequal sharing of electrons Ionic- Cation and Anion bonding (positive and negative charge) Physical Changechange is reversibleno chemical reaction Chemical Changechemical reaction occurred, extremely hard to reverse it Dipole- means two poles :13:56 5/42 Notessolutionsroessler (5/42)

6 Solubility Rule Like Dissolves Like Water can dissolve ionic substances because it has poles with a charge Water does not dissolve covalent substances like oil- no charge :13:56 6/42 Notessolutionsroessler (6/42)

7 Practical Application So if Water can dissolve almost everything except covalent, then how do we remove covalent substances from our skin or clothes? There is a long hydrocarbon (covalent) and a water soluble ionic group :13:56 7/42 Notessolutionsroessler (7/42)

8 Factors Affecting Solubility Agitation- Stir It- molecules are forced to interact more Energy- Increase the temperature- Increase kinetic energy Crush It- Make the particle size smaller- more chance of the solvent particles contacting the solute particles :13:57 8/42 Notessolutionsroessler (8/42)

9 More Terminology Unsaturated- you can put more solute into the solvent Saturated- The maximum amount of solute to solvent Supersaturated-being more concentrated than normally possible and therefore not in equilibrium :13:57 9/42 Notessolutionsroessler (9/42)

10 Biology Connection :13:57 10/42 Notessolutionsroessler (10/42)

11 Electrolytes Electrical Conductivity- ability to conduct electricity Strong electrolyte- ions easily separate- conduct electricity well Weak Electrolyte-ions separate but not as easily- conduct electricity Non electrolyte- do not separate into ions nor do they conduct electricity :13:57 11/42 Notessolutionsroessler (11/42)

12 How the Pickle works Sophomores This is your important TEK Must be a closed circuit to conduct electricity :13:58 12/42 Notessolutionsroessler (12/42)

13 Strong Electrolytes Strong Electrolytes Soluble Salts Strong acids Strong Bases Svante August Arrhenius- the extent to which a solution can conduct an electric current depends directly on the number of ions present Svante August Arrhenius 2/19/ /2/1927 Sweeden :13:58 13/42 Notessolutionsroessler (13/42)

14 Weak versus Strong :13:58 14/42 Notessolutionsroessler (14/42)

15 Biology Connection water, sugar, table salt, carbohydrates, electrolytes (110 mg sodium, 30 mg potassium, 93 mg chloride), high fructose corn syrup, artificial colors, glucose, fructose, and sugar :13:58 15/42 Notessolutionsroessler (15/42)

16 Composition of Solutions Remember to perform stoichiometric calculations you need 1. The nature of the reaction 2. The amounts of chemicals present For solutions we call this Concentration Mathematically it is Molarity :13:59 16/42 Notessolutionsroessler (16/42)

17 Molarity M= Molarity = Moles of solute/ Liters of Solution We write it as 1.0 M, 0.5 M It tells us how strong the solution is :13:59 17/42 Notessolutionsroessler (17/42)

18 Important Concept :13:59 18/42 Notessolutionsroessler (18/42)

19 Lab Conection :13:59 19/42 Notessolutionsroessler (19/42)

20 Dilution Stock Solutions- come concentrated HCl- 12M Water is added to the solution to dilute the solution Moles of Solute after dilution= moles of solute before dilution :14:00 20/42 Notessolutionsroessler (20/42)

21 Dilution in the Lab When making parallel dilutions, use the following formula to calculate the amount of stock solution needed for each dilution: C1 X V1 = C2 X V2 or C1V1 = C2V2 C1 is the concentration of the starting (stock) solution V1 is the volume of starting (stock) solution needed to make the dilution (this is your unknown) C2 is the desired concentration of your final (dilute) solution EOC V1M1=V2M2 V2 is the desired volume of your final (dilute) solution :14:00 21/42 Notessolutionsroessler (21/42)

22 Another look We can also describe solutions in regards to their Mass Percent Mass Percent= (Mass of solute/ Mass of solution) * 100% :14:00 22/42 Notessolutionsroessler (22/42)

23 Mole Fraction Mole Fraction is symbolized by chi or X The ratio of the number of moles of a given component to the total number of moles of solution :14:00 23/42 Notessolutionsroessler (23/42)

24 Molalility Molality is symbolized with an m it describes a solution Relationship of moles of solute to mass of solvent in kg :14:00 24/42 Notessolutionsroessler (24/42)

25 Normality Symbolized by N It is defined as the number of equivalents per liter of solution Equivalents- is defined by the type of reaction that is taking place in the solution acid-base reaction- its 1 mole of Hydrogen Ions H+ Redox reactions- it is 1 mole of reducing/oxidizing electrons :14:01 25/42 Notessolutionsroessler (25/42)

26 Dissolve it Faster Agitate it- Stir it, molecules come in contact with each other more often so they dissolve each other Heat it- Add energy to it, Increase the temperature, Molecules have more energy and interact with each other more frequently Crush It- Increase the surface area so that more molecules interact with each other :14:01 26/42 Notessolutionsroessler (26/42)

27 TAKS Test Pressure does NOT dissolve solids faster Don t fall for it! There are only three Crush It Agitate It Heat It :14:01 27/42 Notessolutionsroessler (27/42)

28 Pressure and temperature Gas Laws Gay Lussac s Law For dissolving Gasses only :14:01 28/42 Notessolutionsroessler (28/42)

29 William Henry 12/12/1774 9/2/1836 England Henry s Law C=kP C is the concentration K is a constant P is pressure Most accurate for dilute solutions of gases that do not dissociate in or react with the solvent :14:02 29/42 Notessolutionsroessler (29/42)

30 Solubility Graphs Be able to interpret information from the graph Which one does the solubility decrease the most as temperature increases? :14:02 30/42 Notessolutionsroessler (30/42)

31 Vapor Pressure Vapor Pressure of a liquid is the equilibrium pressure of a vapor above its liquid (or solid) The pressure resulting from evaporation of a liquid (or solid) above a sample of the liquid (or solid) in a closed container Lowering Vapor pressure depends on number of solutes present in the solution Francois-Marie Raoult 5/10/1830 4/1/1901 French Raoult s Law Psoln= XsolventP solvent :14:02 31/42 Notessolutionsroessler (31/42)

32 Colligative Properties Colligative Propertiesare properties of solutions that depends on the number of molecules and not on their individual properties like size or mass of molecules Freezing Point Depression Boiling Point Depression Osmotic Pressure Vapor Pressure :14:02 32/42 Notessolutionsroessler (32/42)

33 Freezing point depression :14:02 33/42 Notessolutionsroessler (33/42)

34 Boiling Point Depression :14:03 34/42 Notessolutionsroessler (34/42)

35 Osmotic Pressure Osmotic pressure is the pressure which needs to be applied in order to prevent the inward flow of water across a semipermeable membrane :14:03 35/42 Notessolutionsroessler (35/42)

36 Desalination Reverse osmosis- if a solution is in contact with pure solvent across a semipermeable membrane and is subjected to an external pressure larger then its osmotic pressure than reverse osmosis occurs. If your filter is a molecular filter used to remove seawater then you can get freshwater from sea water :14:03 36/42 Notessolutionsroessler (36/42)

37 First Nobel Prize in Chemistry First Nobel Prize in Chemistry (1901) Showed that very dilute solutions follow mathematical laws like gases as well as their behavior Jacobus Henricus van t Hoff 8/30/1852 3/1/1911 Dutch :14:03 37/42 Notessolutionsroessler (37/42)

38 Colloids Colloids are a suspension of tiny particles in a medium Suspension- a mixture in which fine particles are suspended in a fluid where they are supported by buoyancy Buoyancy- the tendency to float in water or another liquid :14:04 38/42 Notessolutionsroessler (38/42)

39 Tyndall Effect Tyndall Effectscattering of light Fog Heterogenous mixtures suspended in liquid :14:04 39/42 Notessolutionsroessler (39/42)

40 Colloid Versus Solution :14:04 40/42 Notessolutionsroessler (40/42)

41 Coagulation To destroy a colloid Add Heat increases the velocities of the colloidal particles- cause particles to aggravate Or add an electrolyte Neutralizes the absorbed ion layers :14:04 41/42 Notessolutionsroessler (41/42)

42 Emulsion- colloid- both phases are liquids Sols/ Gels-colloid in continuous liquid phase with solid suspended in it Foam- colloid gas formed on the surface of a liquid or solid :14:05 42/42 Notessolutionsroessler (42/42)