Solutions and Solubility
Copyright © 200 5 by Pearson Education, Inc. Publishing as Benjamin Cummings
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earning goals
Identi!y the solute and sol"ent in a solution
#e!ine the terms $solubility%, $ma&imum solubility or saturation point%, $precipitate%, 'saturated$, 'unsaturated' and 'supersaturated'
(se solubility cur"es to determine ma&imum ratios o! solute to sol"ent
Calculate the mass o! the precipitate prec ipitate that is !ormed )hen a saturated solution is cooled
E&plain the e!!ect o! temperature on the solubility o! a solid solute in a li*uid sol"ent.
E&plain the e!!ect o! pressure on the solubility o! a gaseous solute in a li*uid sol"ent. s ol"ent.
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21.2 Water and solutions A
solution is a solution is mixture of two or more substances that is homogeneous at the molecular level.
Homogeneous Homogeneous means means
the particles are evenly distributed.
21.2 Water as a mixtu mixture re
+ Muddy water is heterogeneous because it contains larger particles of soil or plant debris.
21.2 Water Water and solutions A
solution contains at least two components: a solvent , and a solute solute..
he
solvent is the part of a mixture that is present in the greatest amount.
Which of these is the solvent!
21.2 Water Water and solutions When
the solute particles are evenly distributed throughout the solvent, we say that the solute has dissolved .
Parts of a Solution SOLUTE – SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) SOLVENT SOLVENT – – the part of a solution that dissolves the solute (usually the greater amount) Solute Solvent ! Solution
Solute Solvent
Example
solid
solid
Metal alloys
solid
liquid
Salt water
gas
solid
Moth balls
liquid
liquid
Alcohol in w ater
gas
liquid
soda
gas
gas
air
"ater is a good solvent
or e&le, sugar and ethanol )hich ha"e one or more 1- groups
such as -Cl shared electron pair goes )ith the more electronegati"e Cl atom/
3aCl 3a4 4 Cl1 orm ion1dipole attraction, positi"e ends o! )ater molecule are attracted to the anions. -o)e"er, -o)e"er, not all ionic compounds c ompounds are )ater
Solubility Solubility is Solubility is
the ma&imum amount o! solute that dissol"es dissol"es in a speci!ic amount o! sol"ent at a gi"en temperature or pressure. e&pressed as grams o! solute in 600 grams o! sol"ent )ater. g o! solute 600 g )ater
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Unsaturated Solutions Unsaturated solutions
contain less than the ma&imum amount o! solute that can dissol"e at a particular temperature. #issol"ed solute
can dissol"e more solute.
7hen a solution is unsaturated its concentration is lo)er than the ma&imum solubility. solubili ty. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
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Saturated Solutions Saturated solutions
contain the ma&imum amount o! solute that can dissol"e at that temperature. ha"e undissol"ed solute at the bottom o! the container precipitate/.
n e&le o! a saturated solution is air.
ir can be saturated saturated )ith )ater. 7e call it humidity8/
Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
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Supersaturated Solutions Supersaturated Supersatura ted solutions
n unstable unstable solution solution that contains contains an amount o! solute greater than the solute solubility, i.e., contains more dissol"ed solute than is possible to be dissol"ed ma&imum solubility/.
lso has undissol"ed undissol"ed solute solute at the bottom o! the container precipitate/. precipitate/.
ne application o! a supersaturated solution is the sodium acetate 9heat pac:.;
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Supersaturated Solutions
2.
7arm the sol"ent so that it )ill dissol"e more, then cool the solution E"aporate some o! the sol"ent care!ully so that the solute does not solidi!y and come out o! solution.
Temperature and Solubility of Solids Temperature
Solubility (g/100 g !"# $%l(s#
&a&"'(s#
0
!)*+
),
!0%
',*0
--
.0%
,!*+
11,
100%
.)*+
1-!
The solubility of most solids (decreases or increases # increases # with an increase in the temperature* ectureP(>
21.2 "olubility graphs
"olubility values for three solutes are plotted in this temperature#solubility graph.
ach line shows how ho w much stuff (%A S"UT# can be dissol2ed in 100 m "3 4AT5 (%A S"6&T# at a bunch of different temperatures*
$ow to get these curves!
Thin7 of an e8periment to determine the solubility cur2es of these salts*
Temperature and Solubility of Solids Temperature
Solubility (g/100 g !"# $%l(s#
&a&"'(s#
0
!)*+
),
!0%
',*0
--
.0%
,!*+
11,
100%
.)*+
1-!
The solubility of most solids increases increases with with an increase in the temperature* ectureP(>
6?
Temperature and Solubility of 9ases Temperature
Solu So lubi bili lity ty (g (g/1 /100 00 g !"# %"!(g#
"!(g#
0%
0*',
0*00)0
!0%
0*1)
0*00,'
.0%
0*0)+
0*00!+
The solubility of gases decreases decreases with with an increase in temperature temperature** ectureP(>
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21.2 "olubility %or
something to dissolve in water, the water molecules need to brea& the bonds between the solute molecules.
Water
dissolves each substance di'erently because the chemical bond strengths between atoms found in di'erent solutes are not the same #
21.2 ()uilibrium
When a solute li&e sugar is mixed with a solvent li&e water, two processes are actually going on continuously.
$ole%ules of solute dissolve and go into solution# $ole%ules of solute %ome out of solution and be%ome &un'dissolved &un'dissolved# #
When the rate of dissolving e)uals the rate of coming out of solution, we say equilibrium has been reached.
earning %hec7 t A0 C, the solubility o! Br is ?0 g600 g - 2. Identi!y the !ollo)ing solutions as either 6/ saturated or 2/ unsaturated. E&plain. °
. D0 g Br added added to 600 g o! )ater )ater at A0 C. °
B. 200 g Br added added to 200 200 g o! )ater at A0 C. °
C. 25 g Br added added to 50 50 g o! o! )ater at at A0 C. °
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Solution . 2
mount o! D0 g Br600 Br600 g )ater is less than the the solubility o! ?0 g Br600 g )ater.
B. 6
In 600 g o! )ater, 600 g Br e&ceeds the solubility solubility o! ?0 g Br )ater at A0 C. °
C. 2
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ffect of Temperature on Solubility >olubility
depends on temperature.
o! most solid solutes increases as temperature o! sol"ent increases.
o! gases decreases as temperature increases.
saturated solution is !ormed on the cur"e, belo) the cur"e the solution is undersaturated.
ffect of Temperature on Solubility
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"olubility curve *ny solution %an be made saturated+ unsaturated+ or supersaturated by %hanging the temperature#
Any mass of solute A:"6 the saturation/solubility cur2e would "65SATU5AT the solution Any mass of solute :"4 the cur2e would U&5SATU5AT the solution
U&;S S"6 U&;SS"6 S"UT S"UT AT AT :"TT"M< or =5%;=;TAT forms as the solution cools
More solute can be dissol2ed to ma7e the solution saturated
earning %hec7 . 7hy could could a bottle o! carbonated drin: drin: possibly possibly burst e&plode/ )hen it is le!t out in the hot sun J B. 7hy do !ish die in )ater that is too )armJ
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Solution .
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Solubility and =ressure enry>s aw states aw states
the solubility o! a gas in a li*uid is directly related to the pressure o! that gas abo"e the li*uid.
at higher pressures, more gas molecules dissol"e in the li*uid.
Boiled )ater tastes bland because dissol"ed gases li:e o&ygen and
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earning chec:
n increase increase in temperature increases increases the solubility solubility o! a solid solute
saturated solution solution becomes becomes unsaturated on heating to dissol"e more o! the solute
n cooling this solution it becomes saturated because solubility decreases on cooling.
-o)e"er, )hen the solute is a gas, the solubility decreases as the temperature rises.
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>olubility Cur"e 7or:sheet
Ke"ision o! Lolar Molume
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Ke"ision o! Lolar Molume
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Ke"ision o! Lolar Molume
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Ke"ision o! Lolar Molume
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Ke"ision o! Lolar Molume