Solubility
Honors ChemistryMrs. Jacobus
Components of a Solution Solute is the substance being dissolved – powder Solvent is the dissolving agent – water
Solute
SolventDissolve
SolubilityThe amount of solute that will dissolve in a given amount of solvent.
Soluble vs. insoluble May vary with solvent
“Like dissolves like”
Polar and Nonpolar• A polar bond is a covalent bond between two
atoms where the electrons forming the bond are unequally distributed
• A nonpolar bond is a covalent bond between two atoms where the electrons forming the bond are equally distributed
Nonpolar Molecule (CH4) Polar Molecule (H2O)
“Like dissolves like”
Two substances with similar intermolecular forces (force between two molecules) are likely to be soluble in each other.
• non-polar molecules are soluble in non-polar solvents
CCl4 in C6H6
• polar molecules are soluble in polar solvents
C2H5OH in H2O
• ionic compounds are more soluble in polar solvents
NaCl in H2O or NH3 (l)
12.2
Factors Affecting Solubility– Temperature – Pressure
Solubility is the amount of solute that will dissolve in a given amount of solvent at a given temperature or pressure.
Factors Affecting the Rate of Dissolution
– Stirring– Temperature– Particle size/Surface
area
A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.
A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.
Sodium acetate crystals rapidly form when a seed crystal isadded to a supersaturated solution of sodium acetate.
12.1
Solubility
Concentration UnitsThe concentration of a solution is the amount of solute present in a given quantity of solvent or solution.
Percent by Mass
% by mass = x 100%mass of solutemass of solute + mass of solvent
= x 100%mass of solutemass of solution
12.3
Mole Fraction (X)
XA = moles of Asum of moles of all components
Concentration Units Continued
M =moles of solute
liters of solution
Molarity (M)
Molality (m)
m =moles of solute
mass of solvent (kg)
12.3
What is the molality of a 5.86 M ethanol (C2H5OH) solution whose density is 0.927 g/mL?
m =moles of solute
mass of solvent (kg)M =
moles of solute
liters of solution
Assume 1 L of solution:5.86 moles ethanol = 270 g ethanol927 g of solution (1000 mL x 0.927 g/mL)
mass of solvent = mass of solution – mass of solute= 927 g – 270 g = 657 g = 0.657 kg
m =moles of solute
mass of solvent (kg)=
5.86 moles C2H5OH
0.657 kg solvent= 8.92 m
12.3
Saturated, Unsaturated & SupersaturatedEx.1) If 10.0 g of KCl is dissolved in 100.0 g of water at
20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? ________________________________________.
Ex.2) If 10.0 g of KClO3 is stirred into 100.0 g of water at 20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? ________________________________________.
Ex.3) If 10.0 g of KClO3 is dissolved in 100.0 g of water at 20.0oC, then would the solution be described asunsaturated, saturated, or supersaturated? ________________________________________.
unsaturated
saturated with about 1 g of undissolved KClO3
supersaturated
Saturated, Unsaturated & SupersaturatedEx.4) If 100.0 g of KI is stirred into 100.0 g of water at
20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? ______________________________________
Ex.5) If 100.0 g of KNO3 is stirred into 100.0 g of water at 60.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? ______________________________________
Ex.6) How many grams of KNO3 will exactly saturate 200.0 g of H2O at 20.0oC? ______________ g
unsaturated
unsaturated
≈70
Temperature and Solubility
Solid solubility and temperature
solubility increases with increasing temperature
solubility decreases with increasing temperature
12.4
Temperature and Solubility
O2 gas solubility and temperature
solubility usually decreases with increasing temperature
12.4
Watch the following video: http://www.youtube.com/watch?v=XSGvy2FPfCw
What kind of a solution is it?
Need more help?
• http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_04&folder=saturated_solutions– Norton tutorial on solubility
• http://www.youtube.com/watch?v=zjIVJh4JLNo&edufilter=d3ViuWqXvxQy1rRgssBz8Q– Basic solubility
• http://www.youtube.com/watch?v=4VltXjR64SU&edufilter=d3ViuWqXvxQy1rRgssBz8Q– Molarity vs. Molality
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