16.1 Properties of Solutions solubility

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Ch. 16 Solutions
16.1 Properties of Solutionssolubility 16.2
Concentrations of Solutionsmolarity, dilutions,
percent solutions 16.3 Colligative Properties of
Solutionsvapor-pressure lowering, freezing point
depression, boiling point elevation 16.4
Calculations Involving Colligative Properties
(SKIP 16.4)
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Vocabulary

• 16.1 solubility, solute, solvent, solution,
  saturated/unsaturated/supersaturated solutions,
  miscible, immiscible
• 16.2 concentration, dilute/concentrated
  solutions, molarity (M), dilution, percent by
  volume, percent by mass
• 16.3 colligative property, vapor pressure
  lowering, boiling point elevation, freezing point
  depression

Key Formulas
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16.1 Properties of Solutions
A sinkhole forms when the roof of a cave weakens
from being dissolved by groundwater and suddenly
collapses. One recorded sinkhole swallowed a
house, several other buildings, five cars, and a
swimming pool! You will learn how the solution
process occurs and the factors that influence the
process.
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Solution Formation

• The compositions of the solvent and the solute
  determine whether a substance will dissolve. The
  factors that determine how fast a substance
  dissolves are
• stirring (agitation)
• temperature
• the surface area of the dissolving particles

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• a) A cube of sugar in cold tea dissolves
  slowly.b) Granulated sugar dissolves in cold
  water more quickly than a sugar cube, especially
  with stirring.

c) Granulated sugar dissolves very quickly in hot
tea.
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• Stirring and Solution Formation
• Stirring speeds up the dissolving process because
  fresh solvent (the water in tea) is continually
  brought into contact with the surface of the
  solute (sugar).
• Temperature and Solution Formation
• At higher temperatures, the kinetic energy of
  water molecules is greater than at lower
  temperatures, so they move faster. As a result,
  the solvent molecules collide with the surface of
  the sugar crystals more frequently and with more
  force.
• Particle Size and Solution Formation
• A spoonful of granulated sugar dissolves more
  quickly than a sugar cube because the smaller
  particles in granulated sugar expose a much
  greater surface area to the colliding water
  molecules.

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Solubility

• The solubility of a substance is the amount of
  solute that dissolves in a given quantity of a
  solvent at a specified temperature and pressure
  to produce a saturated solution.
• Solubility is often expressed in grams of solute
  per 100 g of solvent.
• Some liquids combine in all proportions, while
  others dont mix at all.
• Two liquids are miscible if they dissolve in each
  other in all proportions.
• Two liquids are immiscible if they are insoluble
  in each other.

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Solubility

• A saturated solution contains the maximum
  amount of solute for a given quantity of solvent
  at a given temperature and pressure.

In a saturated solution, the rate of dissolving
equals the rate of crystallization, so the total
amount of dissolved solute remains constant.
An unsaturated solution contains less solute than
a saturated solution at a given temperature and
pressure. A supersaturated solution contains
more solute than it can theoretically hold at a
given temperature.The crystallization of a
supersaturated solution can be initiated if a
very small crystal, called a seed crystal, of the
solute is added.
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• a) A supersaturated solution is clear before a
  seed crystal is added.b) Crystals begin to form
  in the solution immediately after the addition of
  a seed crystal.c) Excess solute crystallizes
  rapidly.

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Factors Affecting Solubility What conditions
determine the amount of solute that will dissolve
in a given solvent?

• Temperature affects the solubility of solid,
  liquid, and gaseous solutes in a solvent
• Both temperature and pressure affect the
  solubility of gaseous solutes.

• The mineral deposits around hot springs result
  from the cooling of the hot, saturated solution
  of minerals emerging from the spring.

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Solubilities can be determined by looking at
tables and charts.
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• Temperature
• The solubility of most solid substances
  increases as the temperature of the solvent
  increases.
• The solubilities of most gases are greater in
  cold water than in hot.
• Pressure
• Changes in pressure have little effect on the
  solubility of solids and liquids, but pressure
  strongly influences the solubility of gases.
• Gas solubility increases as the partial pressure
  of the gas above the solution increases

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FYInot required information

• Henrys law states that at a given temperature,
  the solubility (S) of a gas in a liquid is
  directly proportional to the pressure (P) of the
  gas above the liquid.

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16. 1 Review

• 1. For a given substance, which of the
  following will NOT influence how fast it
  dissolves?
• a) temperature
• b) amount of agitation
• c) molar mass
• d) size of the crystals

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2. The solubility of a substance is often
expressed as the number of grams of solute per a)
100 liters of solvent. b) 1 cm3 of solvent. c)
100 grams of solution. d) 100 grams of solvent.
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3. The solubility of a gas in a solvent is
affected by a) both temperature and pressure. b)
only pressure. c) only temperature. d) both
pressure and agitation.
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16.2 Concentrations of Solutions
Water must be tested continually to ensure that
the concentrations of contaminants do not exceed
established limits. These contaminants include
metals, pesticides, bacteria, and even the
by-products of water treatment. You will learn
how solution concentrations are calculated.
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• The concentration of a solution is a measure of
  the amount of solute that is dissolved in a given
  quantity of solvent.
• A dilute solution is one that contains a small
  amount of solute.
• A concentrated solution contains a large amount
  of solute.

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• Molarity (M) is the number of moles of solute
  dissolved in one liter of solution.
• To calculate the molarity of a solution, divide
  the moles of solute by the volume of the solution.

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• To make a 0.5-molar (0.5M) solution, first add
  0.5 mol of solute to a 1-L volumetric flask half
  filled with distilled water.
• Swirl the flask carefully to dissolve the solute.
• Fill the flask with water exactly to the 1-L
  mark.

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• Making Dilutions
• Diluting a solution reduces the number of moles
  of solute per unit volume, but the total number
  of moles of solute in solution does not change.
• The total number of moles of solute remains
  unchanged upon dilution, so you can write this
  equation.
• M1 and V1 are the molarity and volume of the
  initial solution, and M2 and V2 are the molarity
  and volume of the diluted solution.

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• Making a Dilute Solution

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• To prepare 100 ml of 0.40M MgSO4 from a stock
  solution of 2.0M MgSO4, a student first measures
  20 mL of the stock solution with a 20-mL pipet.
• She then transfers the 20 mL to a 100-mL
  volumetric flask.
• c) Finally she carefully adds water to the mark
  to make 100 mL of solution.

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• Volume-Measuring Devices

volumetric flask
buret
graduated cylinder
pipette
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• Percent Solutions
• The concentration of a solution in percent can be
  expressed in two ways as the ratio of the volume
  of the solute to the volume of the solution or as
  the ratio of the mass of the solute to the mass
  of the solution.

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• Concentration in Percent (Volume/Volume)

Isopropyl alcohol (2-propanol) is sold as a 91
solution. This solution consist of 91 mL of
isopropyl alcohol mixed with enough water to make
100 mL of solution.
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• Concentration in Percent (Mass/Mass)

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16.2 Review

• 1. To make a 1.00M aqueous solution of NaCl, 58.4
  g of NaCl are dissolved in
• a) 1.00 liter of water.
• b) enough water to make 1.00 liter of solution
• c) 1.00 kg of water.
• d) 100 mL of water.

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• 2. What mass of sodium iodide (NaI) is contained
  in 250 mL of a 0.500M solution?
• a) 150 g
• b) 75.0 g
• c) 18.7 g
• d) 0.50 g

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• 3. Diluting a solution does NOT change which of
  the following?
• a) concentration
• b) volume
• c) milliliters of solvent
• d) moles of solute

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• 4. In a 2000 g solution of glucose that is
  labeled 5.0 (m/m), the mass of water is
• a) 2000 g.
• b) 100 g.
• c) 1995 g.
• d) 1900 g.

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16.3 Colligative Properties of Solutions

• The wood frog is a remarkable creature because it
  can survive being frozen. Scientists believe that
  a substance in the cells of this frog acts as a
  natural antifreeze, which prevents the cells from
  freezing. You will discover how a solute can
  change the freezing point of a solution.

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Colligative Properties

• A property that depends only upon the number of
  solute particles, and not upon their identity, is
  called a colligative property.
• Three important colligative properties of
  solutions are
• vapor-pressure lowering
• boiling-point elevation
• freezing-point depression

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• a) In a pure solvent, equilibrium is established
  between the liquid and the vapor.
• b) In a solution, solute particles reduce the
  number of free solvent particles able to escape
  the liquid. Equilibrium is established at a lower
  vapor pressure.

Vapor pressure lowering--The decrease in a
solutions vapor pressure is proportional to the
number of particles the solute makes in solution.
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• a) Three moles of glucose dissolved in water
  produce 3 mol of particles because glucose does
  not dissociate.
• b) Three moles of sodium chloride dissolved in
  water produce 6 mol of particles because each
  formula unit of NaCl dissociates into two ions.

3 moles Na and 3 moles Cl-
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• c) Three moles of calcium chloride dissolved in
  water produce 9 mol of particles because each
  formula unit of CaCl2 dissociates into three
  ions.

3 moles Ca2 and 3 moles 2 Cl- which is 3 moles
Ca2 and 6 moles Cl-
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• Freezing-Point Depression
• The difference in temperature between the
  freezing point of a solution and the freezing
  point of the pure solvent is the freezing-point
  depression.
• The magnitude of the freezing-point depression is
  proportional to the number of solute particles
  dissolved in the solvent and does not depend upon
  their identity.

The freezing-point depression of aqueous
solutions makes walks and driveways safer when
people sprinkle salt on icy surfaces to make ice
melt. The melted ice forms a solution with a
lower freezing point than that of pure water.
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• Boiling-Point Elevation
• The difference in temperature between the boiling
  point of a solution and the boiling point of the
  pure solvent is the boiling-point elevation.
• The same antifreeze added to automobile engines
  to prevent freeze-ups in winter, protects the
  engine from boiling over in summer.
• The magnitude of the boiling-point elevation is
  proportional to the number of solute particles
  dissolved in the solvent.
• The boiling point of water increases by 0.512C
  for every mole of particles that the solute forms
  when dissolved in 1000 g of water.

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16.3 Review
1.Which of the following is NOT a colligative
property of a) vapor-pressure lowering b)
freezing-point depression c) boiling-point
elevation d) solubility elevation
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• 2. Choose the correct word for the space The
  magnitude of each colligative property of
  solutions is proportional to the __________
  solute dissolved in the solution.
• a) type of
• b) number of particles of
• c) molar volume of
• d) particle size of the

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3. The decrease in vapor pressure when a solute
is added to a liquid is due to a) attractive
forces between solvent particles. b) repulsion
of the solute particles by the solvent
particles. c) dissociation of the solvent
particles. d) attractive forces between solvent
and solute particles.
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• 4.You have 500 mL of 1M solutions of NaCl,
  Na2SO4, Na3PO4, and Al2(SO4)3. Which solution
  will have the highest boiling point?
• a) NaCl(aq)
• b) Na2SO4(aq)
• c) Na3PO4(aq)
• d) Al2(SO4)3(aq)

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• Ch. 16What you need to know
•  
• Vocabulary (miscible, immiscible, dilute,
  concentrated)
• Preparing Solutions lab
• Solution formation (stirring, temperature,
  particle size, solute, solvent, solution)
• Solubility (saturated, unsaturated,
  supersaturated g / 100 g solvent)
• Molarity (know this!!)
• Dilution (know this!!)
• solutions (mass, volume)
• colligative properties (vapor-pressure lowering,
  freezing point depression, boiling point
  elevation)

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Practice Problems
1. Use the chart to answer the questions   a)
What is the solubility of NH4Cl at 70?C?     b)
At what temperature is the solubility of KNO3
60g KNO3/100g H2O?    2. A solution has a volume
of 1.75 L and contains 50. g of glucose
(C6H12O6). What is the molarity of the
solution?   3. How many moles of solute are in
380 mL of 1.8 M CaCl2? How many grams is
this?   4. A bottle of the antiseptic hydrogen
peroxide (H2O2) is labeled 3.0 (v/v). How many
mL of H2O2 are in the 600. mL bottle of this
solution?   5. How many grams of K2SO4 would you
need to prepare 1500 g of 4 K2SO4 (m/m)
solution?   6. Why might calcium chloride spread
on icy roads be more effective at melting ice
than an equal amount of sodium chloride?
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16.4 SKIP!!!!!!

• Cooking instructions often call for the addition
  of a small amount of salt to the cooking water.
  Dissolved salt elevates the boiling point of
  water. You will learn how to calculate the amount
  the boiling point of the cooking water rises.

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• Molality and Mole Fraction
• The unit molality and mole fractions are two
  additional ways in which chemists express the
  concentration of a solution.

• The unit molality (m) is the number of moles of
  solute dissolved in 1 kilogram (1000 g) of
  solvent. Molality is also known as molal
  concentration.

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• To make a 0.500m solution of NaCl, use a balance
  to measure 1.000 kg of water and add 0.500 mol
  (29.3 g) of NaCl.

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• Ethlylene Glycol (EG) is added to water as
  antifreeze.

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• The mole fraction of a solute in a solution is
  the ratio of the moles of that solute to the
  total number of moles of solvent and solute.

• In a solution containing nA mol of solute A and
  nB mol of solvent B (XB), the mole fraction of
  solute A (XA) and the mole fraction of solvent B
  (XB) can be expressed as follows.

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