Regents Chemistry Unit 3C Solutions Text Chapter 13 Reference Tables F, G & T Chemists have Solutions!
SOLUTIONS homogeneous mixture (uniform composition throughout) Solute - substance being dissolved (usually present in the lesser amount) Solvent does the dissolving - present in greater amount
Types of Solutions 1) Gas - both solvent/solute are gases ex. Air 2) Solids - 2 or more solids are uniformly spread out ex. alloy- ex. brass = Cu/Zn; steel = iron + carbon 3) Aqueous water is the solvent, (aq) ex. NaCl(aq) 4) Liquid ex. antifreeze
Types of Solutions Con t Miscible ex. Rubbing alcohol and water Immiscible ex. Oil and water
Solubility the ability to dissolve in water UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration Precipitation Dissolved material falling out of solution
shows the dependence of solubility on temperature Solubility Curves
Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temp based on a saturated solution
Saturation A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated. *This is a solution that is at equilibrium. (on the line in Table G)
A solution that contains less solute than a saturated solution under existing conditions is unsaturated. (below the line on Table G) Unsaturated
Supersaturated
Solids vs- Gases Solids are more soluble at... high temperatures. Gases are more soluble at... low temperatures & high pressures
A simple way to convert between units is using the Molarity TRIANGLE. Mole M(mol/L) X Liter
Dilutions Acids are usually acquired in concentrated form and then diluted to the desired concentration, by adding water (aqueous solution). Since moles of acid before dilution = moles of acid after dilution, and moles of acid = M (molarity) x V (volume), then M 1 V 1 = M 2 V 2
Dilution Example How much concentrated 18 M sulfuric acid is needed to prepare 250 ml of a 6.0 M solution? Step 1: Substitute into dilution formula and solve: M 1 V 1 = M 2 V 2 18 M x V 1 = 6.0 M x 250 ml V 1 = 83 ml
Like Dissolves Like depends on the forces of attraction Solute type nonpolar solvent polar solvent Nonpolar soluble insoluble Polar insoluble soluble Ionic insoluble soluble
ppm 100.0 grams of water is evaporated and analyzed for lead. 0.00010 grams of lead ions are found. What is the concentration of the lead, in parts per million? ppm = grams of solute x 1,000,000 grams of solution = (0.00010 g) x 1,000,000 100.0 g = 1.0 ppm (10 6 ) *On Table T If the legal limit for lead in the water is 3.0 ppm, then the water sample is within the legal limits (it s safe and ok)
Concentration by % Mass = Mass of solute (g) (PART) X 100 Mass of Solvent or Solution (g) (WHOLE) A 50.0 gram sample of a solution is evaporated and found to contain 0.100 grams of sodium chloride. What is the percent by mass of sodium chloride in the solution? % mass = 0.100 g X 100 50.0 g = 0.200%
Concentration % Volume = Volume of solute (ml) X 100 Volume of Solvent or Solution (ml) Substitute volume of part divide by volume of whole) in the above equation and multiply by 100 Ex.#1 What is the percent by volume of hexane if 20.0 ml of hexane are dissolved in benzene to a total volume of 80.0 ml? % volume = volume of solute x 100 volume of solution = 20.0 ml x 100 80.0 ml = 25.0%
Solvation - the process of dissolving solute particles are surrounded by solvent particles solute particles are separated and pulled into solution
Dissociation separation of an ionic solid into aqueous ions NaCl(s) Na + (aq) + Cl (aq)
Molecular Solvation -molecules stay intact C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq)
Solvation and Conductivity - + - + - + sugar Non- Electrolyte solute exists as molecules only acetic acid Weak Electrolyte solute exists as ions and molecules salt Strong Electrolyte solute exists as ions only DISSOCIATION
Colligative Properties depend on the number of particles rather than the nature of the particles in the solution. Boiling point and freezing point some of the properties affected.
Freezing Point Depression f.p. of a solution is lower than f.p. of the pure solvent
Boiling Point Elevation b.p. of a solution is higher than b.p. of the pure solvent Solute particles weaken intermolecular forces in the solvent.
Applications salting icy roads making ice cream Antifreeze (ethylene glycol) cars (-64 C to 136 C) fish & insects (have a natural antifreeze)
Colligative Properties con t. # of Particles Nonelectrolytes (covalent: non-metals) remain intact when dissolved 1 particle Electrolytes (ionic-metal +non-metal) dissociate into ions when dissolved 2 or more particles
Boiling point elevation It is proportional to the concentration of dissolved particles 1 mole of particles in solution raises the BP of water by 0.52 C Which solution will have the highest boiling point? KNO 3 Mg(NO 3 ) 2 Al(NO 3 ) 3
Freezing Point Depression It is proportional to the concentration of dissolved particles 1 mole of particles in solution depresses the FP of water by 1.86 C What solution will depress the FP of water the most. AlCl 3 or MgCl 2? Why?