Bio Louis Jacques Mand Daguerre

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Lecture 26
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BioLouis Jacques Mandé Daguerre
Photographs
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Mandé Daguerre 1787-1851

• Scene painter using light to change scene

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photochemistry

• Plastics harden
• Tan your skin
• Paper yellows

Nicephore Niépce inventor
Tar hardens in light
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Copper and silver would react when reacted with
lightIt was a dull and faint image

• Nicephore Niépce died after 3 years.

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Mandé Daguerre by accident placed one of the
copper silver plates in a cabnet .. the next day
the image was bright

• Mercury

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2) 2KI Pb(NO3)2? PbI2 2KNO3a) Synthesisb)
Combustionc) Decompositiond) Single
Replacemente) Double replacement
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1) Fe S ? FeSSynthesisCombustionDecompositio
nSingle ReplacementDouble replacement
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• Br2 2KI ? 2KBr I2
• a) Synthesis
• b) Combustion
• c) Decomposition
• d) Single Replacement
• e) Double replacement

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• Ca(OH)2? CaO H2O
• a) Synthesis
• b) Combustion
• c) Decomposition
• d) Single Replacement
• e) Double replacement

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• Complete the below reaction
• 5) C5H12 O2? ______ _______

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• Complete the below reaction
• Al HCl ? ______ _________

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• Ca F2? _____________
• type of reaction _____________________

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• ) H2O __________ ____________
• type of reaction _____________________

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• A form of rust, iron(III) oxide reacts with
  powdered aluminum to produce molten iron and
  aluminum oxide in a spectacular reaction. Write
  the equation
• __________ _______ ? _______ ___________

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Net ionic equations
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Homework

• Read pages 286 to 289
• do problems 1-12 on page 289

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What is the driving force for chemical reactions?
Lower energy level

• Two of the most basic compounds with the lowest
  energy level that represents an endpoint for many
  chemical reactions include
• H2O CO2

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In order for a chemical reaction to happen there
must be some degree of rearrangement
Notice how not everyone is involved in the
rearrangement There are spectators
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Keeping your eye on the ball is often difficult
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Show salt in water

• To demonstrate how compounds interact, Lets start
  with a simple reaction

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Hydration is the separation of ionic substances
by water

• It is so important that it has three names
• Hydration
• Molecular solvation
• Dissolving
• Disassociation

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Hydration of salt in water
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Hydration of salt in water
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Hydration of salt in water
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Hydration of salt in water
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Hydration of water
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Hydration of water
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Salt in water video
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The way you write this ionic dissociation as an
ionic chemical equation is

• Notice how there are TWO NO3- ions in solution
  and that the charge is designated on each ion

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Electrolytes are ions in solution.

• Water will not carry an electric current unless
  there are electrolytes like salt in the water.
  
• Gatorade has electrolytes of Calcium and
  potassium that are lost during sweating. The
  nerves will actually lose the ability to carry a
  current and you get cramps

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K2S ? 2K S-2

• K2S ?

MgBr2 (NH4)2S FeCl3 Ti(NO3)4 AlCl3
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Basically the ionic compounds are falling apart
like a cookie in water
Why didn't PbI2 dissociate
Only (aq) compounds will dissociate
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• AgNO3(aq) NaCl(aq) ? AgCl(s) NaNO3(aq)

Ag(aq) NO3-(aq) Na(aq) Cl-(aq)
? AgCl(s) Na(aq) NO3-(aq)
Notice how NO3-(aq) and Na(aq) didnt change
from the reactant side to the product side ---
only Ag and Cl really reacted
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Ag(aq) NO3-(aq) Na(aq) Cl-(aq)
? AgCl(s) Na(aq) NO3-(aq)
Unchanged spectator
Unchanged spectator
Unchanged spectator
Unchanged spectator
Ions that dont change during a chemical reaction
are called spectator ions and can be removed from
the equation leaving a
Net Ionic Equation
Ag(aq) Cl-(aq) ? AgCl(s)
Why didnt AgCl dissociate Why isnt it
written Ag Cl-
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These ions did not stay in solution as a hydrate
but precipitated out as a solid all other
chemicals were spectators and uninvolved in the
reaction
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Fe(s) 2AgNO3(aq)? 2Ag(s) Fe(NO3)2(aq)

• Write the ionic equation

Fe(s) 2Ag(aq) 2NO3-(aq) ?
2Ag(s) Fe2(aq) 2NO3-(aq)
SO THE NET IONIC EQUATIONS IS Fe(s) 2Ag(aq)
? 2Ag(s) Fe2(aq)
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The net ionic equation lets you determine if a
chemical reaction takes place

• KCl (aq) NaNO3 (aq)? KNO3 (aq) NaCl (aq)

K(aq)Cl-(aq)Na(aq) NO3-(aq)?
K(aq)NO3 (aq)Na(aq) Cl-(aq)
What kind of reaction must take place in the
above reaction
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Do the 5 problems on the handout
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What if you are predicting a product, you will
have to know if the product is (aq) or (s)
Na2SO4 PbCl2 ? ?
Na2SO4 PbCl2 ? NaCl PbSO4
Na2SO4 PbCl2 ? 2NaCl PbSO4

• The only way to do these problems is if you know
  if an ionic compound in solution is solid or
  ionizes in water (aq) or (s) ????

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• There are rules (The order matters)

Gen chem does not have to memorize this But you
must be able to write them!!!!!!!!!!!!!!!!
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So what this comes down to is knowing what
hydrates (goes into solution) and what does not
All compounds of Group 1 NH4 and NO3- are
soluble They are very reactive and that makes
them ionize and go into solution Group 7 and
SO4-2 are also reactive but not as strong so
while they go into solution there are exceptions
Ag and Pb2 and Ba2 which make group 7 and
SO4 -2 insoluable All CO3- are insoluble
except (as we said) those of Group 1 and NH4.
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Note the arrow group1 N then S then group 7
Soluble
Insoluble CO3- except if bound to group 1 and
NH4

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Some examples of how Group 7 and SO42- have
exceptionsAg is used in film Pb globs in your
brainBa is used in making x-raysall are
insoluble and will pop out of solution in a cloud
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AgNO3 is

• Not soluble

Iodine or another halogen is added to the AgNO3
and you get AgI
Is AgI silver (I) iodide soluble?
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Pb(NO3)2 2 KI ? PbI2 2 KNO3
aq
aq
s
aq
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Pb(NO3)2 2 NaCl ? PbCl2 2 NaNO3
aq
s
aq
aq
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So lets get back to the predicting net ionic
equationproblem
Na2SO4 BaCl2 ?
Na2SO4 aq) BaCl2(aq)? 2NaCl(aq)BaSO4(aq)
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Balancing the electrons on a net ionic equations

• Balance the elements
• Balance the electrons (charges)

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Once you get the simpler net ionic equation you
must make sure that the charges also balance
along with the atoms
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Fe(s) 2Ag(aq)?2Ag(s) Fe2(aq)
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K2SO4(aq) Ba(NO3)2(aq) ? BaSO4 (s) 2KNO3(aq)

• Net ionic equation is
• SO4-2(aq) Ba2(aq) ? BaSO4 (s)

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Finally the net ionic equation allows us to look
at the active part of an equation an determine if
it will occur

• Fe(s) 2Ag(aq) ? 2Ag(s) Fe2(aq)

Is iron metal going to lose 2 electrons to silver
(one each) Which metal is the He man and hold
the electron?
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The activation series