Hindenberg

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Lecture 46
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Hindenberg
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• On may 6th 1937, the German Airship
• Hindenberg was attempting to moor at the
• Naval Air Station in Lakehurst N.J.

The Hindenberg, over nine hundred feet long,
and filled with 7 million cubic feet of hydrogen,
suddenly burst into flames just prior to reaching
the mooring tower.
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• There appears to be no adequate explanation for
  the failure to recognize the test being conducted
  at the time of the accident as
• hazardous. The only explanation offered the
  committee is that NASA officials believed they
  had eliminated all sources of ignition
• and since to have a fire requires an ignition
  source, combustible material, and oxygen, NASA
  believed that necessary and
• sufficient action had been taken to prevent a
  fire.

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Think ahead

• Dont allow others take away your ability to see
  the big picture

Denial aint just a river in Egypt Mark Twain
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Homework

• Read pages 539 to 556
• Problems 1 through 7 on page 556

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Turn in your labs
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• questionnaire

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We know that a pH of 5 means that there is

• 1x10 -5 H3O ions

1x10-9 OH- ions
Because there are about 10,000 times as many H3O
as OH- then there must be an acid around that has
turned the solution thick with Hydronium
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Common pH

• 1 M HCl 0.0
• Lemon juice 2.3
• Coffee 5.0
• Pure Water 7.0
• Blood 7.35-7.45
• Milk of Magnesia 10.5

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• Acids and bases exist as conjugate acid-base
  pairs. The term conjugate comes from the Latin
  stems meaning "joined together"

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Conjugate acid base pair
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Morris is said to be a pitcher just as long as
he is throwing the ball. As soon as he lets go
of the pitch he then becomes a fielder. HNO3
is an acid as long as it has the H to pitch.
But as soon as it throws the H becomes
available to receive an H and is a base.
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HNO3 H2O ? H3O NO3-

• HNO3 is the acid and NO3- is the associated base
  of that acid. This acid and associated base is
  called a conjugate acid base pair.

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Determine the conjugate acid (This is the base
what acid did it come from)
H3O
H2CO3
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Determine the conjugate base for each (This is
the acid what base was created)  
OH--
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Notice how a strong acid has a weak conjugate base
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The stronger the acid the weaker the conjugated
base

• The weaker the acid the stronger the conjugated
  base

If something is good at losing a H it is clearly
not good at holding on to something
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Identify the conjugate acid and bases for the
below examples

• Example 1
• H2SO4 H2O ? H3O HSO4-
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• Example 2
• HCl H2O ? H3O Cl-
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• Example 3
• H2O NH3 ? NH4 OH-
•  

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We have seen how water can act as both an acid
and a base
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When a molecule has the capability of being able
to act as either a base or a acid it is called
amphiprotic

• Water does this pretty well. When H2O accepts a
  H it becomes a rather aggressive acid as H3O
• When H2O donates a H it becomes a rather
  aggressive base as OH-

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A good example of an amphiprotic molecule is the
cabbage indicator.

• In an acid solution, the indicator acts like a
  base and accepts a hydrogen then it turns pink
• In a basic solution, the indicator acts like a
  acid and gives up a hydrogen then it turns green

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In a way the indicator is kind of like a utility
man in base ball. It can do pretty much
everything

• He can hit or run or field

In chemistry we call something that works as both
a acid and base really well a buffer
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A buffer can act as a acid or a base

• Why is this important

Most biological systems are sensitive to changes
in pH or acidity
a buffer will gobble up and neutralize any stray
H or if there are any bases around it will
readily neutralize a base by donation a H
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HCO3 is a classic buffer found in the body

• HCO3 acid ? H2CO3
• HCO3 base ? CO3-

Buffers are Atomic bodyguards
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quiz
when confronted by an acid buffers grab the H
and when confronted by a base donates the H. in
both cases the buffer HCO3 ends up in a stable
state while rendering the acid or base
neutralized
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Quiz 46
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Review quiz