Solutions Ch.13

(13-1) Mixtures Suspension: appears uniform, but separates out when settled –Ex: muddy water Colloid: small particles suspended in a solvent & doesn’t settle out –Ex: milk

Solution Solvent: substance in which solute dissolves Solute: substance dissolved Aqueous: soln in which solvent is H 2 O

Concentration Amt. of solute in a specific amt. of solvent or soln –Low conc. = dilute soln –High conc. = concentrated soln

Measuring Conc. Molarity (M) = mols of solute L of soln Molality (m) = mols of solute kg solvent

Molarity Practice What’s the molarity of a KCl soln that has a V of 400 mL & contains 85 g of KCl? 1.List known V = 400 mL m = 85 g

Molarity Practice 2.Convert into appropriate units 400 mL x 1 L = 0.4 L 1000 mL 85 g KCl x 1 mol = 1.14 mol KCl 74.6 g 3.Substitute & solve M = mols = 1.14 mol = 2.85 M L 0.4 L

Molality Practice How many mols of NaF are required to make a 0.30 m soln using 0.6 kg of water? 1.List known m = 0.30 kg solvent = 0.6

Molality Practice 2. Write eq., substitute, & solve m = mols  mols = (m)(kg) kg = (0.30 m)(0.6 kg) = 0.18 mol

Separating Mixtures Filtration Evaporation Centrifuge Distillation –Drinking water from sea water Chromatography –Separating dyes in ink

(13-2) Solubility Max amt. of a chemical that will dissolve in a given quantity of solvent at a specified T Soluble: can be dissolved Insoluble: does not dissolve Rxn of KI soln & Pb(NO 3 ) 2 soln

Shellfish form their shells from CaCO 3. The organism secretes Ca 2+ from cells in contact w/ seawater, which contains dissolved CO 2, some of which is present as CO The ions combine to give a precipitate of CaCO 3.

Kidney stones are generally also insoluble calcium cmpds such as calcium carbonate, calcium phosphate, or calcium oxalate.

Henry’s Law Solubility of a gas in a liquid is directly proportional to the partial P of that gas –Pop bottle w/ CO 2 Gas solubility depends on P & T –Inc. P, inc. solubility –Inc. T, dec. solubility

Saturated Containing amt. of solute specified by solubility Supersaturated: containing more than the amt. of solute specified by solubility

Miscible Liquids that dissolve in 1 another –Similar polarity Immiscible: liquids that will not dissolve in each other –Ex: oil & water

(13-3) Conductivity Ability to conduct electric current Electrolyte: conducts electricity –Ex: NaCl dissolved in H 2 O –Ionic Nonelectrolyte: does not conduct –Ex: C 6 H 12 O 6 dissolved in H 2 O –Covalent

Electrolytes Strong electrolyte: almost completely dissociates (separates into fragments) in soln –Ex: NaCl(s) + H 2 O(l)  Na + (aq) + Cl - (aq) Weak electrolyte: small % dissociates in soln –Ex: NH 3 (aq) + H 2 O(l)  NH 4 + (aq) + OH - (aq)

Hydronium Ion H ion bonded to a H 2 O molecule (H 3 O + ) Hydration: H 2 O molecules surround each ion in a soln

(13-4) Colligative Properties Physical properties that are dependent on the # of solute particles present rather than the particle identity

Boiling-point Elevation Difference b/w the bp of a soln & a pure substance Freezing-point depression: difference b/w the fp of a pure solvent w/ a soln