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Unformatted text preview: salt water 40 g undisso lved NaCl Na+ and Cl- io ns: leave the crystal disso lve in water 24 g undisso lved NaCl Nr. of ions disso lving 12 g undissoved NaCl Nr. of ions returning Nr. of Nr. of ions ions disso lving returning 4 g undissoved NaCl Nr. of Nr. of ions = ions dissolving returning Dynamic equilibrium has been established NaCl(s) 3 NaCl(aq) Chemistry 101 Chapter 12 AT EQUILIBRIUM Rate at which ions leave the crystal Rate at which ions return to the crystal Rate of disso lving Rate of crystallization NaCl(s) NaCl(aq) · The composit ion o f the solut ion no longer changes
· A saturated solut ion has been obtained CONCLUSIONS:
o · At 20 C no more than 36 g of NaCl can disso lve in 100 g of water. Solubilit y of a substance: Ø is the amount of substance that can be disso lved in 100 g of so lvent at a given temperature. o Ex: The solubilit y of NaCl at 20 C is 36 g NaCl/100 g water Saturated Solut ion: Ø A so lut ion containing the maximum amount of solute that can be disso lved in a given amount of solvent at a given temperature o Ex: At 20 C, a solution containing 36 g of NaCl disso lved in 100 g of water Unsaturated Solut ion: Ø A so lut ion containing less than the maximum amo unt of so lute that can be disso lved in a given amount of so lute at a given temperature o Ex: At 20 C, a solution containing 28 g of NaCl disso lved in 100 g of water (8 g more of NaCl can be disso lved) Supersaturated Solut ion: Ø A so lut ion containing more disso lved so lute that a saturated solut ion 4 Chemistry 101 Chapter 12 FACTORS AFFECTING SOLUBILITY
· Why do some substances mix and others do not ?
· There are 2 main factors that determine the so lubilit y o f a substance in a given so lvent. I. TENDENCY TOWARD DISORDER (Tendency toward a state of lower energy) Substances have a natural tendency to mix. Ex: all gases are miscible in each other This factor favors the disso lving process NOTE: If this were the only factor, all substances would have unlimited so lubilit y in each other. II. RELATIVE FORCES OF ATTRACTION BETWEEN SOLUTE AND SOLVENT SPECIES There are 3 types of forces of attraction: 1. Between solute ® ¬ solvent Favor the disso lving process particles 2. Between solute ® ¬ solute Works against the disso lving process particles 3. Between solvent ® ¬ solvent Works against the disso lving process particles CASE 1: The forces of attraction between solute and solvent particles The forces of attraction between This happens...
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