Transcript Chapter 13 Solutions

Properties of Solutions: Most things in life are solutions. Get with the
program.

Do Now:
 Clear desk except for a writing utensil-
Intermolecular Forces Quiz

Define the following words with a neighbor:
 Solvent:
 Solute:
 Aqueous solution:
 Entropy:
 Spontaneous:

Predict the resulting reaction for Ammonium
Nitrate and Water

Do we expect this process to be endothermic
or exothermic? Why?
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Why is this reaction surprising?

What can we ask for the aim today?
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How is the ability of a substance to form a
solution affected?
 Types of I.M.F in solution process
 Natural tendency of substances to mix/spread when
not restrained

Why is the mixing of gases a spontaneous
process?
 No energy input from outside the system

Why is it important to discuss entropy in
solution?
 Increase in entropy is favored in solutions

Explain why NaCl mixes in water and not
gasoline.

Three types of intermolecular attraction in
solution formation:
 Solute-solute: interactions between molecules of
solute must be overcome to disperse solute
 Solvent-solvent: interactions between solvent
molecules must be overcome to make way for solute
 Solvent-solute: occur as particles mix

In terms of intermolecular attraction, what must
be true in order for a solution to form?
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In terms of intermolecular attractions, explain
why heptane and pentane can mix.

Write a paragraph explaining why NaCl is able to
dissolve in water. Include the following terms:
 Solvent-solute
 Solute-solute
 Solvent-solvent
 Ion-dipole attraction

Define:
 Solvation:
 Hydration:

As we experienced in our demo, solution
processes generally are accompanied by:

How might we be able to determine how the
interactions in the solution influence
enthalpy?

Formulate an equation to calculate ∆Hsoln
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
Do Now:
Write a paragraph explaining why NaCl is able
to dissolve in water. Include the following
terms:
 Solvent-solute
 Solute-solute
 Solvent-solvent
 Ion-dipole attraction

Predict for each of the three types of
interactions whether or not they are
endothermic or exothermic. Explain your
reasoning.

Why is enthalpy useful to us in determining
extent of reaction?

How is forming a solution different than a
chemical reaction?

Define dissolution:
What does this suggest for our aim?

On the molecular level, explain the
interactions of solute and solvent as
concentration increases.

Define the following terms with a neighbor:
 Saturation:
 Unsaturated:
 Supersaturation:
 Solubility
How does solubility of gas relate to intermolecular forces?

How do we
differentiate
between miscible
and immiscible?

How can we alter
hexane to make is
miscible? Explain
in terms of
attraction.
**Hint: how does the number of carbons affect
solubility in water?
DO NOW:
 Predict whether each of the following substances is
more likely to dissolve in the solvent carbon
tetrachloride or water:





C7H16
Na2SO4
HCl
I2
Arrange the following in order of increasing solubility
in water (explain your reasoning *psst.. Please actually write
the reason in your notebook.**):
 c5H11OH, c5H12, c5H11Cl, c5H10(OH)2

As the world is
evolving, the
number of
habitable lakes
for wildlife is
slowly
declining.

Predict the trend between pressure and
solubility.
 Can you think of an example?

At equilibrium, rate of gas molecules entering
and leaving solution is equal.
 Exert pressure: what happens to the rate at which
molecules are colliding with the surface?

How can we relate this to the partial pressure
of gas?
 Solubility of gas in a liquid solvent increases in
direct proportion to partial pressure of gas.
Relationship between pressure and gas
solubility:
Sg = kPg
Sg= solubility of the gas in the solvent (usually
expressed as molarity)
Pg= partial pressure of the gas over solution
k= proportionality constant (Henry’s Law
Constant)
**k depends on solute, solvent, and temp.
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
Calculate the concentration of CO2 in a soft
drink that is bottled with a partial pressure of
4.0 atm over the liquid at 25 degrees celcius.
The Henry’s law constant for CO2 in water at
this temperature is 3.4 x 10-2 mol/L-atm

As temperature
increases, the
solubility of most
solid solutes
increases. How do
you think gas
solubility is effected
by temperature?

Why do bubbles form on the inside of the
cooking pot when water is heated on a stove,
even though the water temperature is well
below the boiling point?

How can we differentiate between mass
percentage, ppm, and ppb?

When would we use ppm or ppb?

IE: toxic concentrations expressed in ppm or
ppb:
 Max allowable concentration of arsenic in drinking
water is 0.010 ppm. How do we express this in
grams?

A solution is made by dissolving 13.5 g of
glucose in 0.100 kg of water. What is the mass
percentage of solute in this solution?

A 2.5 gram sample of groundwater was found
to contain 5.4 microliters of zinc 2+. What is
the concentration of Zn 2+ in ppm?

Do Now:
 Calculate the mass percentage of NaCl in a
solution containing 1.50 g of NaCl in 50.0 g of
H2O.
 A commercial bleaching solution contains 3.62%
by mass sodium hypochlorite (NaOCl). What is the
mass of NaOCl in 2.50 kg of bleaching solution?
3.0 Molar
3.0 Molal

How do we express mole fractions?
 IE: Solution contains 1.00 mol of HCl + 8.00 mol of
H2O. What is the mole fraction of HCl?

How do we express Molarity?
 IE: What is the molarity of a solution with 0.50 mol
of solute in 0.250 L solution?

How do we express molality?
 IE: 0.200 mols of NaOH is mixed with 0.500 kg of
H2O. What is the concentration?

How can we differentiate between molality
and molarity?
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**Note: when water is solvent, the 2
numbers will be very similar. Why?
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Why do we use molality when varying
temperature of solution?
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A solution is made by dissolving 4.35 g of
glucose in 25 mL of H2O @ 25 degrees
celcius. Calculate the molality.

What is the molality of a solution made by
dissolving 36.5 g of Naphthalene (C10H5) in
425 g of Toluene (c7H8)?

Sometimes it is necessary to interconvert
units when given a different unit.

IE: An aqueous solution of HCl contains 36%
HCl by mass.

A solution with a denistry of 0.876 g/mL
contains 5.0 g of Toluene and 225 g of
Benzene. Calculate the molarity.

Remember that worksheet you were given
for homework? Time to go take another look
at it…

Do now:
 A solution containing equal masses of glycerol
(C3H8O3) and water has a density of 1.10 g/ml.
Calculate:
▪ The molality of glycerol
▪ The mole fraction of glycerol
▪ The molarity of glycerol

Define Colligative Properties:
 Properties of solvents that depend on total
concentration of solute particles present
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Give Examples of Colligative Properties:
 Vapor-Pressure Lowering
 Freezing Point Lowering
 Boiling Point Elevation
 Osmotic Pressure
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Redefine the following words in terms of
vapor pressure:
 Vapor Pressure:
 Volatile:
 Non-volatile:
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Describe what would happen if you added a
nonvolatile solute to a volatile solvent.
Explain this visual.
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Vapor pressure of solution containing nonvolatile solue/volative solvent is proportional to
solvent concentration
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How do we express this qualitatively?
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IE: Vapor pressure of water @ 20 degrees Celsius
is 17.5 torr. If temp is held constant and sugar is
added, mol fraction of water is XH2O= 8.00.
How does the addition of glucose effect the
vapor pressure?

Glycerine- a nonvolatile nonelectrolyte with a
density of 1.26 g/ml is used to make a
solution with 50.0 mL glycerine with 500.0
mL water. At 25 degrees Celsius, the vapor
pressure of water is 23.8 torr and density is
1.00 g/ml.

The vapor pressure of pure water at 110
degrees Celsius is 1070 torr. A solution of
ethylene glycol and water has a vapor
pressure of 1.00 atm at 110 degrees Celsius.
What is the mole fraction of ethylene glycol?
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Do Now:
 Calculate the Vapor Pressure of water above a
solution prepared by adding 22.5 g of lactose
(C12H22O11) to 200.0 g of water at 338 K. (pure
water = 187.5 torr)
 Calculate the mass of propylene glycol (C3H8O2)
that must be added to 0.340 kg of water to reduce
the vapor pressure by 2.88 torr at 40 degrees
Celsius. (pure water = 55.3 torr)
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Using prior knowledge, how might we relate
the concept of an ideal gas to that of an ideal
solution?

Explain what this means for solute-solute,
solvent-solvent, and solute-solvent
interactions.

** Be aware, not all solutions are “ideal”
will be discussed in later chapters.
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If the addition of non-volatile solute lowers
vapor pressure, how is the boiling point
effected?

How can we represent the increase in boiling
point numerically?
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IE: NaCl is dissolved in water. A 1 molal solution
is created. Calculate the boiling point elevation
of the solution.

Summarize: A solute dissolved in water causes
the boiling point to increase by 0.51 degrees
celsius. Does this necessarily mean that the
concentration of the solute is 1.0 m? Explain.
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How do we determine the freezing point of a
liquid?
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How is freezing point effected when creating
solutions? Explain.

How might we calculate the change in
freezing point?

IE: Automotive antifreeze consists of
ethylene glycol, CH2(OH)CH2(OH), a
nonvolatile nonelectrolyte. Calculate the
boiling point and greezing point of a 25.0
mass % solution of ethylene glycol in water.
(Kb= 0.51 C/m) (Kf= 1.86 C/m)

Which of the following solutes will produce
the largest increase in boiling point upon
addition to 1 kg of water and why
 Co(NO3)2
 2 mol of KCl
 3 mol of ethylene glycol (C2H6O2)

Define semipermeable

Define Osmosis
 Why does osmosis take place?

*note: rate at which solvent passes from less
concentrated solution (lower solute, higher
solvent) to more concentrated solution is
greater than the rate in the opposite direction

Define Osmotic Pressure:

Similar to ideal gas law:
∏ = (n/V)RT
∏ = osmotic pressure
V= volume of the solution
n= number of moles of solute
R = ideal gas constant
T = temperature in Kelvin
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How can we change the equation to include
Molarity?
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Using these diagrams and the concept of
osmotic pressure, label and define which of
these are isotonic, hypotonic, and hypertonic.
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Describe what would happen if a red blood
cell was placed in a solution that is hypertonic
relative to the intracellular solution.
 Crenation: process in which a cell shrivels
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Describe what would happen if the cell is
hypotonic relative to intracellular fluids.
 Hemolysis: process of cell repture

The average osmotic pressure of blood is 7.7
atm @ 25 degrees celsius. What molarity of
glucose will be isotonic with blood?

What is the osmotic pressure at 20 degrees
Celsius of a 0.0020 M sucrose solution?
(C12H22O11)

Any of the four colligative properties can be
used to determine molar mass:
 1. Freezing Point Depression/ Boiling Point
Elevation:
▪ A solution of unknown solute was prepared by dissolving
0.250 g of the substance in 40.0 g of CCl4. The resultant
boiling point of the solution was 0.357 degrees higher
than that of the pure solvent. Calculate the molar mass.
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Osmotic Pressure:
 The osmotic pressure of an aqueous solution of a
certain protein was measured to determine the
proteins molar mass. The solution contained 3.50
mg of protein dissolved in sufficient water to form
5.00 mL of solution. The osmotic pressure of the
solution at 25 degrees celsius was found to be 1.54
torr. Calculate the molar mass.

Camphor (C10H16O) melts at 179.8 degrees
Celsius and it has a large Kf= 40.0 C/m. When
0.186 g of an organic substance of unknown
molar mass is dissolved in 22.01 g of liquid
camphor, the freezing point is found to be 176.7.
What is the molar mass?

A sample of 2.05 g of polystyrene of uniform
polymer chain length was dissolved in enough
toluene to form 0.100 L of solution. The osmotic
pressure of the solution was found to be 1.21 kPa
at 25 degrees Celsius. Calculate the molar mass.