Will a precipitate form if solutions of potassium sulfate and barium nitrate are combined? If so, write the net ionic equation for the reaction.

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• Will a precipitate form if solutions of potassium
  sulfate and barium nitrate are combined? If so,
  write the net ionic equation for the reaction.
• Will a precipitate form if solutions of potassium
  nitrate and magnesium sulfate are combined? If
  so, write the net ionic equation for the
  reaction.

1 1 1 . 3
quiz points
1. Answer Yes
Ba2(aq) SO4 2-(aq) ? BaSO4(s)
2. Answer No
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Introduction to Colligative Properties Ch 13-2

• Objectives
• List four colligative Properties
• Calculate Freezing Point Depression, Boiling
  Point Elevation

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Defined

• Colligative properties are properties of a
  solution which are dependent only on the number
  of particles in solution, not their nature.

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There are four colligative properties

1. Lowering of the Vapor Pressure of a Solution
2. Osmosis
3. Boiling Point Elevation
4. Freezing Point Depression

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Fun Facts

• Anti-freeze, for the car radiator, is often
  marketed as "winter-summer protection." This
  isn't because the company is being nice and
  giving you a two-for-one deal. It is because you
  get one when you get the other. They cannot be
  separated.

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BP elevation and FP depression

• Boiling point elevation is exactly what its name
  says. When you make a solution, the solution will
  begin to boil at a temperature ABOVE that of the
  pure solvent.
• Freezing point depression is also exactly what
  its name says. The solution will begin to freeze
  at a temperature BELOW that of the pure solvent.

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FP depression (Dtf)

• the difference in FP of pure solvents is
  proportional to the molal concentration of the
  solution.
• The freezing point of a 1 m solution of any
  non-electrolyte is found to be 1.86C lower than
  the FP of water.
• Water 1 m solution has FP of -1.86C
• Water 2 m solution has FP of -3.72C

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Molal Freezing-Point Constant (Kf) -1.86C/m

• The freezing point depression of the solvent in a
  1-molal solution of a nonvolatile, non-eletrolyte
  solution

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Calculate the Dtf

• Dtf Kfm
• Dtf is in C
• Kf is in C/m

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example

• Given the FP of a solution -0.23C
• What is the molality of the solution?

Dtf Kfm
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Molal Boiling Point constant (Kb) 0.51 C/m

• The boiling point elevation of the solvent in a
  1-molal solution, of nonvolatile, nonelectrolyte
  solute.

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Dtb Kbm

• Dtb Kbm
• Dtb is in C
• Kb is in C/m
• Pg 451 3 If the BP elevation of an (aq) solution
  is 1.02C, what is the molality of the solution?

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Vapor Pressure

• Many pure liquids (and even some solids) will
  evaporate to a slight extent at almost any
  temperature. This will produce a slight gas
  pressure above the pure liquid.

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This is called vapor pressure and was discovered
by John Dalton.
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Vapor Pressure

1. Imagine this a rigid-walled container which is
   empty (a vacuum).
2. Now, introduce into it some pure liquid water.
   Some, not all, of the liquid evaporates into the
   gas state.
3. In a short time, there will come an equilibrium
   between the gas and the liquid. This pressure can
   be measured and it is called vapor pressure.

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The vapor pressure is dependent on temperature
only.
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In a solution, say sugar in water, the vapor
pressure of the solution is lower than that of
the pure solvent at the same temperature.
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Fun Facts

• Certain fish in the Artic have anti-freeze
  proteins in their blood. Many cities sprinkle
  salt on icy roads to melt the ice. You put salt
  on the ice when making homemade ice cream. All
  this is done to lower the freezing point below
  the zero degrees Celsius of pure water.

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Fun Facts

• Osmosis is an important biological function and,
  when it is forced to run in reverse (called
  "reverse osmosis" as if that's a suprise) it's an
  important source of fresh water.

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OSMOSIS Osmotic Pressure

• The movement of water

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• Osmosis is the net movement of water in the
  direction opposite to the diffusion of solute.
• It typically will involve the use a
  semi-permeable membrane.

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Osmosis

• The movement of water from an area of high
  concentration to low concentration.
• Osmosis ceases when the H2O is equal on both
  sides of a membrane.
• Semi-permeable membranes permit the passage of
  some components of a solution.
• ??Examples cell membranes, cellophane.

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Osmotic Pressure

• ??The movement can support pressure of a column
  of water.
• ??External pressure can make the heights equal.

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Osmotic Pressure

• Osmotic pressure, p, is the pressure required to
  stop osmosis

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Osmosis

• Isotonic solutions two solutions with the same p
• Hypotonic solutions a solution of lower p than a
  hypertonic solution.
• Hypertonic solutions a solution of higher p than
  hypotonic solution.
• Examples of osmosis Cucumber placed in NaCl
  solution loses water to shrivel up and become a
  pickle.

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Homework

• Page 459
• 19, 20, 21, 25, 30

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