Transcript Chapter 12

Chapter 12
Solutions
Dr. S. M. Condren
Solution
Solutions, in chemistry, homogeneous
mixtures of two or more substances.
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Solute
The substance that is present in
smallest quantity is said to be dissolved
and is called the solute. The solute can
be either a gas, a liquid, or a solid.
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Solvent
The substance present in largest
quantity usually is called the solvent.
The solvent can be either a liquid or a
solid.
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Types of Solutions
• Gaseous solutions - air
• Liquid solutions - drinks
• Solid solutions - steel
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Coke lists as its ingredients as: “carbonated
water, high fructose corn syrup and/or
sucrose, caramel color, phosphoric acid,
natural flavors, caffeine”.
What is the solvent?
What are the solutes?
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Miscible and Immiscible Liquids
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Solution Terminology
saturated
• solution containing undissolved solute in
equilibrium with the solution
unsaturated
• solution containing less than the maximum
amount of solute
supersaturated
• solution containing more solute than is
normally allowed
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Saturated Solution
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Ion-Dipole Attraction
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Dissolving of Ionic Solid in Water
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Temperature Changes with Solution Process
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Pressure Changes with Solution Process
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Molarity
The number of moles of solute per liter of
solution.
molarity => M
moles of solute
M = -------------------liter of solution
units => molar = moles/liter = M
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Parts per Million
#g of solute
#mg of solute
ppm = --------------------- * 106 = ----------------------#g of solution
#kg of solution
#micro-L solute
ppm = ----------------------#Lof solution
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Molality
• number of moles of solute particles (ions or
molecules) per kilogram of solvent
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Boiling Point Elevation
DT = Tfinal - Tinitial
(DTb = bpsolution - bppure solvent)
DTb = kb x m
where kb => boiling point elevation constant
m => molality of all solutes in solution
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Freezing Point Depression
DT = Tfinal - Tinitial
(DTf = fppure solvent - fpsolution)
DTf = kf x m
where kf => freezing point depression
constant
m => molality of all solutes in solution
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The freezing point of water is lowered
proportional to the number of solute species
present. In identical experimental circumstances,
if NaCl is replaced with CaCl2 as a solute in
water, how will the freezing point compare?
higher temperature with CaCl2
lower temperature with CaCl2,
no difference
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Why is it better to leave the “anti-freeze” in
your cooling system during the summer?
it might get very cold
it keeps the engine from over heating
saves time and money
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