Post on 29-Nov-2014
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The interaction between solventand solute determines how much asubstance will dissolve.
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Solubility = How much solutedissolves in a certain amount ofsolvent
Example- the solubility of sugar is 203g/100mL at 20°C
Insoluble compound = has asolubility less than 0.1g/100mL.
Temperature also determineshow much a substance willdissolve.
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A saturated solution containsthe maximum amount of solutefor a given quantity of solvent at agiven temperature and pressure.
An unsaturated solutioncontains less solute than asaturated solution.
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In a saturatedsolution, the rate ofdissolving equalsthe rate ofcrystallization, sothe total amount ofdissolved soluteremains constant.
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Some liquids combine in all proportions,while others don’t mix at all.
–Two liquids are miscible ifthey dissolve in each other inall proportions.
–Two liquids are immiscible if they areinsoluble in each other.
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Oil and water are immiscible.
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Vinegar and oil are immiscible.
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Temperature affects the solubility ofanything.
Pressure affects the solubility of a gas.
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Temperature
–The solubility of a solidincreases as the temperatureof the solvent increases.
–The solubility of a gasdecreases as temperatureincreases.
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The mineral depositsaround hot springsresult from thecooling of the hot,saturated solution ofminerals emergingfrom the spring.
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A supersaturated solution containsmore solute than it can theoreticallyhold at a given temperature.
Crystallization of the extra solute can be initiatedif a very small crystal of the solute is added.
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A supersaturated solution is clear before aseed crystal is added.
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Crystals begin to form in the solutionimmediately after the addition of a seedcrystal.
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Excess solute crystallizes rapidly.
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Pressure
Changes in pressure have little effecton the solubility of solids and liquids.
Gas solubility increases as thepartial pressure of the gasabove the solution increases.
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Honors only
Henry’s law states that at a giventemperature, the solubility (S) of a gasin a liquid is directly proportional to thepressure (P) of the gas above the liquid.
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The factors that determine howfast a substance dissolves are
•stirring (agitation)
•Temperature (also affects how muchdissolves)
•the surface area of the dissolvingparticles
A cube of sugar in cold tea dissolves slowly.
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Granulated sugar dissolves in cold water morequickly than a sugar cube, especially with stirring.
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Granulated sugar dissolves very quickly in hot tea.
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At higher temperatures moleculesmove faster.
Water molecules surround andremove the solute particles fromthe solid more quickly.
Particle Size and Solution Formation
A spoonful of granulated sugardissolves more quickly than a sugarcube because the smaller particles ingranulated sugar expose a muchgreater surface area to the collidingwater molecules.
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Stirring and Solution Formation
Stirring speeds up the dissolvingprocess because fresh solvent (thewater in tea) is continually brought intocontact with the surface of the solute(sugar).
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16.1 Section Quiz.
1. For a given substance, which of the followingwill NOT influence how fast it dissolves?
a. temperature
b. amount of agitation
c. molar mass
d. size of the crystals
16.1 Section Quiz.
3. The solubility of a gas in a solvent is affectedby
a. both temperature and pressure.
b. only pressure.
c. only temperature.
d. both pressure and agitation.