Solution Chemistry

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UNIT IX

• Solution Chemistry
• Lesson 1

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Introduction

• Solution Chemistry is the study of chemical
  reactions that occur in solutions
• Reactions in solutions are chemists favourite
  type of reactionsbecause of how easy and
  convenient they are.
• Compare to
• Reactions in the gas phase are complicated? need
  special containers (air-tight)
• Solid reactions ? very slow or do not occur at
  all

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Introduction

• In this unit, we will deal with liquid or solid
  solutes that are dissolved in liquid solvents
• (not pure solids, liquids or gases)

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Lets remember some definitions

• Solution
•  
• Solvent
•  
• Solute

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Solutions and solubility

• Saturated solution
•  
• Unsaturated solution
• Solubility

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Saturated Vs Unsaturated
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Solutions and conductivity

• Do all solutions conduct electricity?
• How do we know?

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Requirements to conduct electricity

• Experiments tell us that you need
• Electrical charge to be transferred in the
  solution in order to produce electricity.
• IONS carry electrical charge!

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Requirements to conduct electricity

• IONS carry electrical charge!
• Therefore, Ionic compounds can conduct
  electricity
• NaCl(aq)
• Can covalent compounds conduct electricity?
• CS2(aq)

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THE CONDUCTIVITY OF AQUEOUS SOLUTIONS

• A conducting solution contains ions the greater
  the concentration of ions, _____________the
  conductivity.
• A compound made up of a METAL and NONMETAL is
  IONIC, and forms a conducting solution in water
  because it breaks into ________
• A substance made up of a NONMETAL and a NONMETAL
  is COVALENT, and will NOT form a conducting
  solution in water because it stays as a molecular
  compound.

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NaCl (Ionic) in water
The "" and "-" ions are now free to move around.
The "" ions would be attracted to a negative
electrode and the "-" ions would be attracted to
a positive electrode. In this way, the ionic
solution conducts a current. 
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What else can conduct electricity??

• ACIDS and BASES form conducting solutions in
  water.
• Why?
• Because they can break into ions!
• HCl
• NaOH

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What else can conduct electricity??

• ACIDS and BASES form conducting solutions in
  water.
• 1- Think of acids as any compounds that starts
  with H
• 2- Think of bases as any compounds that end with
  OH
• Exception if a compound starts with Carbon and
  ends with OH. It is an alcohol, not a base and
  cant conduct electricity.
• Ex CH3OH (cant conduct electricity)

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What else can conduct electricity??

• Metals (only in liquid or aqueous phases) can
  conduct electricity
• Examples Na(l), Cu(aq), Ag(aq)
• Ex Na(s) cant (because it is a solid!!!)
• Na(l) or Na(aq) can

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So what cant conduct electricity??

• 1) Non-metals
• 2) Covalent compounds
• 3) Organic compounds(usually start with Carbon-C-
  and contain hydrogens)
• Ex CH3OH, C14H10
• CH3COOH (exception)
• 4) Solids

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TO CONDUCT or NOT TO CONDUCT??? This is the
question.....

• CONDUCT DOESNT CONDUCT
• Metals non
  metals
• ionic solid
• acids covalent
• bases organic compounds
• CH3COOH (exception)
•  
• http//www.youtube.com/watch?vUHYWIM8AbPE

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Think about this

• For solutions to form, and to mix chemical
  compounds together when adding a solute to a
  solvent to make a solutionbonds need to break
  and new bonds need to form!
• So, we need to remember the intermolecular forces
  that hold molecules together.

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Back to forces between molecules

• Van der Waals Forces
• THREE main types
• DIPOLE-DIPOLE FORCES
• LONDON FORCES
• HYDROGEN BONDING
• All are caused by dipoles!

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• A. DIPOLE-DIPOLE FORCES
• Caused by dipoles
• Dipole A temporary separation of charges, where
  more electrons are found on one side on the atom
  than the other side.
•  
• Dipole-Dipole Forces a permanent dipole results
  from atoms with different ELECTRONEGATIVITY!

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Dipole-Dipole forces

• Ex
• HCl
  H2O

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B. LONDON FORCES

• London Forces
• LONDON FORCES exist for everything!!!
• London forces strength increases as the of
  electrons is increased.
• Ex Does He or Xe have a stronger london forces
  bond?

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• C. HYDROGEN BONDING
•  
• Hydrogen Bond strong dipole dipole attraction
  between molecules containing a H N, H O, or H
  F bond
• (because N,F and O are highly electronegative)
•  intermolecular bond (between molecules)
• strongest van der Waals bonds but still weaker
  than covalent and ionic
•  

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• C. HYDROGEN BONDING
•  
• Hydrogen Bond strong dipole dipole attraction
  between molecules containing a H N, H O, or H
  F
• Ex
• NH3 and NH3 
  H2O and H2O
• Hint Look for HF or any molecule having OH or NH
  in its formula

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Comparing strengths of bonds

• IONIC BOND ??DIPOLE DIPOLE LONDON FORCE
• Intramolecular Intermolecular
•  
• Ionic bonds will always be stronger than any
  intermolecular bond.
• Remember, London forces strength increases with
  the increased number of electrons.

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Explain this

• Boiling temperatures
• ICl 97 C (70 electrons)
• Br2 59 C (70 electrons)

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Homework

• Page 198,199
• Questions 6,7
• Question 8 (do a,c,e, etc)
• Question 9
• Page 202, 203, 204
• Question 11 and Question 12
• Question 14 and Question 16