Solubility Section 8.5. Solubility When we dissolve a solute in water, there is a point where no...
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Transcript of Solubility Section 8.5. Solubility When we dissolve a solute in water, there is a point where no...
Solubility When we dissolve a solute in water, there is a point
where no more will dissolve
Saturated solution - a solution containing the maximum quantity of a solute at specific temperature and pressure conditions look for the presence of undissolved solids in the solution
Solubility – the concentration of a saturated solution of a solute at a specific temperature and pressure Units for solubility are usually grams of solute per 100
mL of solvent (g/100mL)
Unsaturated solution = a solution containing less than maximum quantity of a solute at specific temperature and pressure conditions
Supersaturated solution = a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances
Other Important Terms
Solubility
SATURATED SOLUTION
no more solute dissolves
UNSATURATED SOLUTIONmore solute
dissolves
SUPERSATURATED SOLUTION
becomes unstable, crystals form
increasing concentration
Solubility tables (pg. 324) ionic compounds are listed as having
either high or low solubility at SATP (25°C and 100 kPa)
anions paired with particular cations have either: High solubility OR Low solubility
Solubility Categories High solubility = with a maximum
concentration at SATP (standard ambient temperature and pressure) of greater than or equal to 0.1mol/L
Low solubility = with a maximum concentration at SATP of less than 0.1mol/L
Insoluble = a substance that has a negligible solubility at SATP
Solubility of Solids Solubility of a solid changes with
temperature Higher solubility at higher temperatures
in industry, the solute is isolated from many solutions by evaporating the solvent
this increases the concentration of a solution and once it is greater than the solubility, the solute crystallizes (precipitates) out
Solubility Curve = a graph of solubility versus temperature
Solubility Curve of Solids (pg. 394) Solubility is most
affected by temperature The line shows you how
much solute can dissolve in 100g of water at a particular temperature.
A concentration on the line is a saturated solution
Concentrations above the line are supersaturated
Concentrations below the line are unsaturated
What can I do with a solubility curve? Calculating the amount of
solute that needs to be added to a solution to make saturate it.
Calculating the amount of solute that will crystallize out of solution when the solution is cooled.
per100 gH2O
Classify as unsaturated, saturated, or supersaturated.
80 g NaNO3 @ 30oC unsaturated
45 g KCl @ 60oC saturated
50 g NH3 @ 10oC unsaturated
70 g NH4Cl @ 70oC supersaturated
So sat. pt. @ 40oC for 500 g H2O = 5 x 66 g = 330 g
120 g < 330 g unsaturated
saturation point @ 40oC for 100 g H2O = 66 g KNO3
Per 500 g H2O, 120 g KNO3 @ 40oC
(A) Per 100 g H2O, 100 g Unsaturated; all
soluteNaNO3 @ 50oC. dissolves; clear
solution.
(B) Cool solution (A) very Supersaturated; extraslowly to 10oC. solute remains in solution;
still clear.
Describe each situation below.
(C) Quench solution (A) in Saturated; extra solute an ice bath to 10oC. (20 g) can’t remain in
solution, becomes visible.
Solubility of Gases Gases have a higher solubility at lower
temperatures
Think: Pop glass of cola sitting in the refrigerator as
compared to one sitting on the kitchen counter
Can of pop is also stored under pressure Increased pressure = increased solubility
Solubility Graph
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517
0 10 20 30 40 50 60 70 80 90 100
Solubility vs. Temperature for Solids
Sol
ubili
ty (
gram
s of
sol
ute/
100
g H
2O)
KI
KCl
20
10
30
40
50
60
70
80
90
110
120
130
140
100
NaNO3
KNO3
HCl NH4Cl
NH3
NaCl KClO3
SO2
shows the dependence
of solubility on temperature
gases
solids
Solubility of Sodium Acetate
Temperature (oC)
025 50 75 100
Sol
ubili
ty(g
/100
g H
2O)
50
100
150Supersaturated
solution
Unsaturated solution
Saturated
Video Clip
Charles H.Corwin, Introductory Chemistry 2005, page 378
A single crystal of sodium acetate, NaC2H3O2, is dropped into a
supersatureated solution
The small crystal causes extensivecrystallization, and eventually
the solute forms a solid mass of NaC2H3O2.