Chapter 12 Solutions

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Chapter 12 Solutions
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12-1 Types of Mixtures

• Solutions focus of chapter
• homogeneous mixture of two or more substances in
  a single phase.
• Particles are very small
• Solute substance being dissolved
• Solvent substance doing the dissolving
• 9 types of solutions possible How?
• Ex
• Cannot be separated by simple filtration
• Do not separate upon standing
• Alloy special solution of metals
• Ex
• Terms Soluble capable of dissolving
• Insoluble - not capable of
  dissolving

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Solute
A solute is the dissolved substance in a solution.
Salt in salt water
Sugar in soda drinks
Carbon dioxide in soda drinks
Solvent
A solvent is the dissolving medium in a solution.
Water dissolving salt
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Solvents
Solvents at the hardware store
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Solutions, Colloids, Suspensions
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Concentrated vs. Dilute
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Suspensions and Colloids
Suspensions and colloids are NOT solutions.
Suspensions The particles are so large that they
settle out of the solvent if not constantly
stirred. Heterogeneous Ex Muddy water Can be
filtered
Colloids The particle is intermediate in size
between those of a suspension and those of a
solution. emulsions, foams sols, gels
Heterogeneous Microscopic scale
under a microscope Homogeneous Macroscopic
scale
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The Tyndall Effect
Colloids scatter light, making a beam visible.
Solutions do not scatter light.
Which glass contains a colloid?
colloid
solution
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Types of Colloids
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Electrolytes and Non-electrolytes
Electrolyte

• A substance whose aqueous solution conducts
• an electric current.

Non-electrolyte

• A substance whose aqueous solution does not
• conduct an electric current.

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DEMO Try to classify the following substances as
electrolytes or non-electrolytes

• Pure water
• Tap water
• Sugar solution
• Sodium hydroxide solution
• Hydrochloric acid solution
• Lemon Juice solution
• Ethyl alcohol solution
• Pure sodium hydroxide-solid

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ELECTROLYTES
NON-ELECTROLYTES

• Tap water (weak)
• NaOH solution
• HCl solution
• Lemon Juice (weak)

• Pure water
• Sugar solution
• Ethanol solution
• Pure NaOH

Why do some compounds conduct electricity in
solution while others do not?
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Electrolytes vs. Nonelectrolytes
The ammeter measures the flow of electrons
(current) through the circuit.

• If the ammeter measures a current, and the bulb
  glows, then the solution conducts.

• If the ammeter fails to measure a current, and
  the bulb does not glow, the solution is
  non-conducting.

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Solutes Electrolytes vs. Non-electrolytes

• Ionic materials dissolved
• Dissociation - the separation of ions. The ions
  are already present at the beginning due to the
  ionic bond.
• Ex Dissociation NaCl
• Na 1Cl-1 H2O? Na (aq) 1 Cl (aq)
  -1
• Polar(covalent) materials dissolved in water
• Ionization- the formation of ions.
• Ex Ionization HCl
• HCl H2O ? H 1 (aq) Cl -1 (aq)

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Dissolution of sodium Chloride
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Compare and Contract Dissociation and Ionization

• Compare

• Contrast

• Both produce ions in solution
  

• Dissociation deals with ionic materials
• Ionization deals with polar covalent materials

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Solute-Solvent interactions

• General Rule Like dissolves like
• Polar dissolves polar
• Ex water and HCL
• non-polar dissolves non-polar
• Ex acetone and Styrofoam
• Polar also dissolves ionic
• Ex water and HCl
• Terms Hydration, immiscible, miscible

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12-2 The Solution Process

• Factors affecting (explained in terms of
  increasing) the rate of dissolution (making a
  solution)
• Increasing surface area, stirring or shaking,
  temperature- increase in kinetic energy
  Increase the rate of dissolution.
• Solution equilibrium dissolving and
  crystallizing occur at the
• same rate in a closed system.
• Solid Liquid Energy and
• Liquid Energy Solid
• term Dissolution

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Saturation of Solutions

• A solution that contains the maximum amount of
  solute that may be dissolved under existing
  conditions is saturated.
• A solution that contains less solute than a
  saturated solution under existing conditions is
  unsaturated.
• A solution that contains more dissolved solute
  than a saturated solution under the same
  conditions is supersaturated.

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Solubility - The amount of a substance required
to form a saturated solution with a specific
amount of solvent at a specified temperature.
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1. Which salt is least soluble at 0ºC? a.
K2Cr2O7 b. KClO3 c. Ce2(SO4)3 d. KNO3 _____ 2.
When 50 grams of potassium chloride, KCl, is
dissolved in 100 grams of water at 50ºC, the
solution can correctly described as a.
Saturated b. Unsaturated c. Supersaturated ____
_ 3. A solution containing 80 g or KNO3 In 100
g of water at 10 oC is a. Unsaturated b.
Saturated c. Supersaturated   _____ 4. At
approximately what temperature does the
solubility of sodium chloride, NaCl, match the
solubility of potassium dichromate, K2Cr2O7? a.
60ºC b. 83ºC c. 50ºC
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• 5. A solution of potassium chlorate, KClO3, has
  20 grams of the salt dissolved in 100 grams of
  water at 70 ºC. Approximately how many more grams
  of the salt can be added to the solution before
  reaching the saturation point?
• a 10 grams
• b. 80 grams
• c. 60 grams
• 30 grams
• ______ 6. When 30 grams of potassium nitrate,
  KNO3, is dissolved in 100 grams of water at 20
  ºC, the solution can be correctly described as
• a. unsaturated
• supersaturated
• saturated
• _____ 7. At what temperature will 20 g of KClO3
• create a saturated solution.
• a. 63 oC
• b. 30 oC
• c. 80 oC
• _____ 8. A beaker containing 80 grams of lead(II)
  nitrate, Pb(NO3)2, in 100 grams of water has a
  temperature of 30 ºC. Approximately how many
  grams of the salt are undissolved, on the bottom
  of the beaker?
• a. 80 grams
• b. 14 grams

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9. When 20 grams of potassium chlorate, KClO3,
is dissolved in 100 grams of water at 80 ºC, the
solution can be correctly described as a.
unsaturated b. supersaturated c.
saturated _____ 10. How many grams of sodium
nitrate, NaNO3, are soluble in 100 g of water at
10 ºC? a. 40 grams b. 80 grams c. 10 grams d.
100 grams _____ 11. Which salt is LEAST soluble
at 50 ºC? a. Ce2(SO4)3 b. KClO3 c.
K2Cr2O7 d. KNO3 _____ 12.Which of these salts
decreases in solubility as the temperature
increases. a. KClO3 b. K2Cr2O7 c.
Ce2(SO4)3 d. KNO3
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Henrys Law

• Law Solubility of a gas is directly
  proportional to the partial pressure of that gas
  on the surface of the liquid.
• Increase P, increase the solubility of the gas in
  a liquid.
• Decrease P, decrease the solubility of the gas in
  a liquid
• Ex Carbonated drink
• Term Effervescence

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Factors Effecting Solubility

• The solubility of MOST solids increases with
  temperature.
• The rate at which solids dissolve increases with
  increasing surface area of the solid.
• The solubility of gases decreases with increases
  in temperature.
• The solubility of gases increases with the
  pressure above the solution.

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Therefore
Solids tend to dissolve best when

• Heated
• Stirred
• Ground into small particles

Liquids tend to dissolve best when

• The solution is cold
• Pressure is high

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Effects of temperature on a gas solute

• Increase temp, decrease gas solubility
• The increase in k.e. causes the particles to move
  faster and out of solution.
• Chart pg 408 Look at SO2 H2S CO2

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Heat of Solution
The Heat of Solution is the amount of heat energy
absorbed (endothermic) or released (exothermic)
when a specific amount of solute dissolves in a
solvent.
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Enthalpies (Heat) of Solutions

• Enthalpy of solution net amount of energy
  absorbed or released when a specific amount of
  solute dissolves in solvent.
• Dissolving is a physical process
• Water could be written on the arrow.
• LiCl H2O H2O ? Li (aq) Cl - (aq)
  37 kJ Exothermic
• Negative enthalpy value (Heat of solution
  value)
• Negative indicates exothermic
• 20.33 kJ KI H2O ? K (aq) I - (aq)
  Endothermic
• Positive enthalpy value (Heat of solution
  value)
• Positive indicates endothermic
• Review assignments 2 and 3

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Concentration of Solution s

• Concentration - A measure of the amount of
• solute in a given amount of solvent or solution

Grams per liter - the mass of solute divided by
the volume of solution, in liters
Molarity - moles of solute divided by the volume
of solution in liters
Molality moles of solute divided by kilogram of
solvent
Parts per million the ratio of parts (mass) of
solute to one million parts (mass) of solution
Percent composition - the ratio of one part of
solute to one hundred parts of solution,
expressed as a percent
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Making a Molar (M) Solution

• M mol solute
• 1 L solution
• How do you make a .5M NaCl solution?
• Determine the amount of solute needed.
• ?g NaCl .5mol x 58.44 g
  29.22g____
• 1 L soln mol
  L solution
• Place measured amount (29.22g NaCl)in a
  volumetric flask
• Dissolve completely in a small amount of the
  solvent
• Shake or heat if needed.
• Raise the solvent volume to EXACTLY 1 Liter.

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Making a molal (m) solution

• m moles solute
• 1 kg solvent
• How do you make a .5m solution of NaCl?
• Determine the amount of solute needed.
• ?g NaCl .5mol x 58.44 g 29.22g
• 1 kg solvent mol
  kg solvent
• Place exactly 1 kg of solvent in the volumetric
  flask and add the measured amount of solute 29.22
  g)

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Molar (M) vs. molal (m)

• Molar solution exactly 1 liter of solution is
  made
• molal solution more than 1 liter (kg) of
  solution is made

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Molarity (M)

• What is the Molarity of 3.50 L of solution
  containing 62.5 g KCl?
• Molarity moles or amount
• Liters volume
• ? mol 62.5 g KCl____________________
  
• L 3.50 L soln

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Molarity

• 2. What is the Molarity of a solution with 45.8
  g of NaOH dissolved in enough water to make 450.8
  mL of solution?
• Molarity moles or amount M
• Liters volume
• ? mol 45.8 g NaOH x ________ x _______
• L 450.8 mL soln

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Molarity

• 3. How many moles of CaBr2 are dissolved in
  250.0 mL of a 3.00 M solution of CaBr2?
• ? mol CaBr2 250.0 mL x __L__ x
  __3.00mol__
• 
  1000 mL 1L

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Molarity

• 4. What mass of zinc acetate, Zn(C2H3O2)2, will
  remain behind if 86.0 mL of a 0.800 M solution of
  Zn(C2H3O2)2 is allowed to evaporate?
• ? g Zn(C2H3O2)2 86.0 mL soln x ______ x ______
  x______

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Molarity

• 5) What volume of a 2.50 M LiCl solution is
  needed for a reaction that requires 220.0g of
  LiCl?

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molality (m)

• 1. What is the molality of a solution containing
  18.2 g HCl and 250.0 g of water?
• molality moles solute
• kg solvent
• ? mol HCl 18.2 g HCl x __________ x
  ___________
• kg water 250.0 g H2O

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molality

• 2. How many grams of NaCl are needed to prepare
  a 1.0 m solution using 250. grams of solvent?
• ? g NaCl .250 kg solvent x ________ x
  ________
• 
  

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molality

• 3. How many grams of AgNO3 are needed to prepare
  a 0.125 m solution in 250.0 mL of water?
  (Remember, for water1g1mL)
• ? g AgNO3 250.0 mL AgNO3 x _______ x _______ x
  ________
  

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molality

• 4. What would be the molality of a solution in
  which 294.3 g H2SO4 was dissolved in 1.000 kg
  H2O?
• molality moles solute
• kg solvent
• ? mol H2SO4 g H2SO4 x
  ____________ m
• kg H2O 1.000 kg H2O