Mullis1 Water: The Universal Solvent Polarity makes water special. O atom is an electron “hog” in the covalent bond it forms with 2 H atoms. Water has a positive end and a negative end. This makes it a good solvent for ionic solids. O H H Slightly positive Slightly negative

Mullis2 Solutions Same as a homogeneous mixture Solvent = substance that takes in, or dissolves, another substance Solute = substance that is taken in, or dissolved by the first substance The 3 phases of matter can be paired together in 9 ways to make solutions.

Mullis3 Solutions and phases of matter Solute (dissolved)(in) SolventExample Gas O 2 in N 2 - Air GasLiquidCO 2 in water GasSolid Hydrogen fuel storage LiquidGasWater in air Liquid Acid in water (vinegar) LiquidSolid Amalgam dental fillings (Hg in Ag) SolidGasMothballs in air SolidLiquidSalt water Solid Metal alloys - jewelry

Mullis4 Factors which affect solution rate and solubility Solution rate: –Temperature –Particle size –Movement Solubility: –Temperature –Pressure

Mullis5 Solubility Solids: Increased temp increases solubility. Gases: Solubility in water decreases when temperature increases. Gases: Increased pressure increases solubility. More fizz in a soda bottle if you store with lid on (increased pressure) and in the refrigerator (decreased temperature).

Mullis6 Concentration Relationship between solute and solvent: Concentration = volume solute/volume solvent Relative concentration of solutions: 1.Unsaturated : More solute can be dissolved at a given temp. and pressure. May be dilute or concentrated. 2.Saturated : Maximum solute a solvent will dissolve at a given temp. and pressure. 3.Supersaturated : More than the maximum solute a solvent will dissolve at a given temp. and pressure. (Usually obtained by heating a saturated solution to very high temp and cooling slowly.)

Mullis7 Concentration Concentration is the amount of solute dissolved in an amount of solution. Molar concentration is called Molarity, or M. M = moles of solute volume of solution in L If 2.0 moles NaCl is dissolved in 1 L of solution, its concentration is “two molar” and is expressed as 2.0 M NaCl.

Mullis8 Steps to make a 1 M solution Example: 1 M NaOH solution 1.Calculate the mass needed. 1 mol NaOH g NaOH = g NaOH 1 mol NaOH 2.Measure this amount of NaOH into a beaker, then dissolve in some solvent to dissolve it. 3.Pour the solution into a 1.0 L volumetric flask. 4.Rinse the weighing beaker with more solvent and add to the flask. 5.Add solvent until the solution meets the line indicating 1.0 L. 6.Stopper the flask and swirl, mix thoroughly.

Mullis9 Molality Molal concentration is called molality, or m. m = moles of solute mass of solvent in kg If 0.50 moles NaCl is dissolved in 1 kg of solution, its concentration is “zero point five molal” and is expressed as 0.50 m NaCl g = 1 kg. For water, 1 g = 1 ml 1kg = 1000 ml = 1 L

Mullis10 Molality Example Molality is used when studying properties of solutions related to vapor pressures and temperature changes. The expression for concentration using m is unaffected by changes in temperature. What is the molality of a solution of 3.73g KCl in 100 g water? 3.73 g KCl 1 mol KCl = 0.05 moles KCl g KCl m = 0.05 moles KCl = 0.5 m KCl solution kg H 2 O

Mullis11 Molarity Example To produce 23.4 g of K 2 CrO 4 from 6.0 M K 2 CrO 4, what volume of the solution is needed? Given: 23.4 g K 2 CrO 4 needed concentration of solution = 6 moles K 2 CrO 4 per 1 L Want: volume of K 2 CrO 4 in solution 23.4 g K 2 CrO 4 1 mol K 2 CrO 4 = mol K 2 CrO g K 2 CrO mol K 2 CrO 4 1 L = L K 2 CrO 4 soln 6 mol K 2 CrO 4

Mullis12 Molality example How much iodine (in grams) must be added to prepare a m solution of iodine in CCl 4 if g of CCl 4 is used? Given: m = m I 2 Want: mass of solute in g solvent = g CCl 4 = kg I 2 = g/mol mol I 2 = x mol I 2 1 kg CCl kg CCl 4 (0.480 mol I 2 )(0.100) = x = mol I mol I g I 2 = 12.2 g I 2 1 mol I 2

Mullis13 Suspensions and Colloids Remember: A solution is a homogeneous mixture. Some mixtures are not solutions—It depends on the size of the particles. Large particles usually don’t make homogeneous mixtures. The names of 2 types of mixtures with large particles are suspensions and colloids.

Mullis14 Suspensions A mixture in which some particles will settle out is a suspension. Gravity will eventually make large particles sink. Particles are large enough to be filtered out. Examples: Muddy water and salad dressing. Particles are large enough to reflect light, so a beam of light will be visible in a suspension.

Mullis15 Comparing mixtures Solution = homogeneous, small particles Suspension = heterogeneous, large particles Colloid = in-between suspension and solution. –Is not completely homogeneous. –Examples: fog, homogenized milk, toothpaste.

Mullis16 Colloids How can you tell is a mixture is a colloid? A beam of light will be visible when shone through a colloid (like a suspension). Particles do not separate or settle out after standing.

Mullis17 Colloids: 5 types Sol –Solid is dispersed in solid or liquid. –Examples: Clay, toothpaste, red glass Gel –Long particles that trap liquid inside. –Examples: Jam, jelly, gelatin dessert, hair gel Aerosol –Solid is dispersed in air. –Examples: Fog, some hair sprays Foam –Gas is dispersed in liquid. –Examples: Marshmallows, whipped cream Emulsion –Liquid is dispersed in liquid. –Examples: Milk, butter, some cosmetics

Mullis18 Comparing mixtures Solution = homogeneous, small particles Suspension = heterogeneous, large particles Colloid = in-between suspension and solution. –Is not completely homogeneous. –Examples: fog, homogenized milk, toothpaste.

Mullis19 Solutes: Electrolytes Electrolyte = Substance that dissolves in water to give a solution that conducts electricity Mobile charged particles conduct electricity (ions) Soluble ionic compounds are electrolytes (Na + and Cl - ) Many acids are electrolytes (HCl =>H 3 O + and Cl - )

Mullis20 Solute-Solvent Interactions Like dissolves like Polar dissolves polar Water + NaCl Nonpolar dissolves nonpolar CCl 4 + motor oil Immiscible liquids (oil and vinegar) –Do not mix –Liquid solutes and solvents that are not soluble in each other Miscible liquids (gas and oil) –Mix –Liquids that dissolve freely in one another in any proportion

Mullis21 Henry’s Law Solubility of gas in liquid The solubility of a gas is directly proportional to the partial pressure of that gas on the surface of the liquid. Soda bottle: –High pressure at the surface while the bottle is closed, so lots of CO 2 in the liquid –Open bottle, pressure on surface lowers to room atmosphere and CO 2 leaves the liquid High pressure = High gas concentration Low pressure = low gas concentration