Things I am collecting

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Things I am collecting

• Article analysis IV
• Molarity Packet
• Molarity by Dilution WS
• Review
• Please put in separate piles

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Chem Matters

• Chem Matters Articles by Topic
• Solutions
• Quest for a clean drink
• Salting Roads
• Forensics of Blood

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Equilibrium

• Big name-- easy idea!

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Chemical Reactions

• You have a system made up of a bunch of
  molecules.
• Energy is absorbed to break bonds.
• Molecules combine to form new compounds
  (releasing energy).

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Collision Theory

• Molecules must bang together
• with enough energy (activation energy)
• in the right orientation (just the right way)
• for a reaction to occur

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Potential Energy Diagram

• Ea activation energy. This is the minimum
  amount of energy necessary to make the reaction
  happen.
• Top of the hill
• Activated complex- (transition state)

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Reverse Reactions

• Once you have a bunch of the new compound the
  new compound wants to go back to being the old
  compound.

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In short- the products become reactants and have
to find a way to get back up over the hill
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Put those two ideas together and you have
EQUILIBRIUM

• 1. Reactants combine to make a products.
• 2. Products like to break apart and turn back
  into the reactants.
• 3. There is a point where the two reactions
  happen and you can't tell that any reactions are
  occurring (equilibrium).

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Think about a swimming pool.(Phase Changes)

• What happens in the summer when it is really hot?
• What happens when it is raining?
• What is happening when the level of the water
  doesnt change?

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In a closed system

1. Net transfer of molecules from the liquid state
   to the vapor state
2. The amount of the substance in the vapor state
   becomes constant
3. The equilibrium state is achieved.

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Rate of Reaction

• Depends on the properties of the reactants (size
  and reactivity)
• Depends on the conditions of the system

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Factors affecting Reaction RateWrite about how
each affects the kinetic energy of the reactants.

1. Temperature
2. Concentration
3. Particle Size (surface area)
4. Agitation

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Iodine/ Vit C demo
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Particle Size Demo
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So.. What exactly is equal at equilibrium??

• Rateforward rxn Ratereverse rxn
• Law of Chemical Equilibrium
• There is no net change in the actual amount of
  the compounds.
• Be careful!! The rate is equal
• the amount is probably not equal!!

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Changes with time in the rates of reactions.

• This looks the same no matter what the products
  and reactants are!!

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Equilibrium Position

• The equilibrium position indicates the relative
  concentration of the products and reactants at
  equilibrium.
• A B -----gt AB
• Can also be the reverse reaction.
• AB -----gt A B
• We draw a wacky double arrow shows to show what
  side of the equation is favored (has more).
• A B AB
• Size Matters!!

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LeChateliers Principle

• If a change is imposed on a system at
  equilibrium, the position of the equilibrium will
  shift in a direction will reduce the change.

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Things we can mess with--

• Concentration- if a component is added to a
  reaction system at equilibrium, the equilibrium
  position will shift in the direction that lowers
  the concentration of that component. If a
  component is removed, the opposite happens.
• H2 F2 ------gt 2HF
• Add this -------? get more of this
• get more of this ?------- Add this

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Temperature

• Treat energy as a reactant in an endothermic
  reaction and a product in an exothermic reaction.
  
• Predict the direction of the shift in the same
  way as when an actual product or reactant is
  added.
• 2H2 O2 ? 2H2O 483kJ

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Pressure- only matters with gasses!

• 2SO2(g) O2(g) ? 2SO3(g)

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Volume

• How about changing the volume of the container??
• Decreasing the volume of the reaction container
  will cause the equilibrium to shift towards the
  side of the reaction with the fewest number of
  gas molecules.

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Demo
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Equilibrium Constant

• Equilibrium Expression Is a ratio of the rates
  of reaction.
• aA bB lt-- gt cC dD
• Keq Cc Dd or Products
• Aa Bb Reactants

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State of Matter does matter

• Reactants or products that are
• solids (s) or liquids (l)
• are not put into the equilibrium expression
• ONLY gasses (g) and
• aqueous solns (aq)
• Are included in the equilibrium expression!!

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Lets Practice!

• Write the equilibrium expression for the
  following reactions.
• H2 F2 lt------gt 2HF
• N2 3H2 lt-------gt 2NH3

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Answers

• H2 F2 lt------gt 2HF
• Keq HF2
• H2 F2
• b. N2 3H2 lt-------gt 2NH3
• Keq NH32
• N2 H23

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Example- Write the equilibrium expression

• CaCO3 (s) Heat ?-? CaO (l) CO2(g)

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What does Keq tell us??

• It tells us which side of the equation is favored
  (will we get more products or reactants?).
• Keqgt1 Products favored, Spontaneous
• Keqlt1 Reactants favored, Nonspontaneous

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Here- watch this!!

• http//cwx.prenhall.com/petrucci/medialib/media_po
  rtfolio/text_images/066_LeChateliersPr.MOV