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Torricelli

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Take the pressure off and the gas will leave the solution. Henry's Law ... acid is an unstable molecule that shoots a hydrogen atom without an electron loose ... – PowerPoint PPT presentation

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Title: Torricelli


1
Torricelli
Laws of motion Thermometer Telescope Compass
Galileo
  • Torricelli served as Galileo's secretary from
    1641 to 1642

Galileo died 8 Jan 1642
Barometer was invented in 1643
2
Check homework
  • Make sure that you can
  • Answer the questions
  • Do all the word problems
  • Do the word problems on handout 40
  • Ideal gas law handout
  • Handout 28

3
Return papers
4
When you first place a molecule in a solution
then if the solution can be dissolved it will go
into solution
unsaturated
5
At equilibrium there are as many red molecules
going into solution as there is red molecules
going out of solution
saturated
6
At equilibrium the amount of solute going into
solution equals the amount of solute going out of
solution
  • Solubility
  • equilibrium

7
If you cool a substance down or if some of the
solvent evaporates off then a molecule must come
out of solution then it is considered
temporally supersaturated until equilibrium is
again reached
8
  • Is carbon tetrachloride, CCl4, soluble in water?
  • Is dimethyl ether, CH3OCH3, soluble in water?
  • Is ethanol, CH3CH2OH, soluble in water?
  • Is propane, CH3CH2CH3, soluble in water?


9
  • Keeping in mind that "Like Dissolves Like", which
    of the following compounds would be
  • the most soluble in a nonpolar solvent such as
    carbon tetrachloride, CCl4?
  • A) H2O
  • B) CH3OH
  • C) CH3CH2CH2CH2CH2OH
  • D) CH3CH2CH2OH

10
NaCl 35.7g NaCl in 100 g H2O at 0OC
  • NaOH 42.0 g in 100 g H2O at 0OC
  • FeCl3 74.4g in 100 g H2O at 0OC
  • MgSO 22.0 g in 100 g H2O at 0OC
  • C6H12O6 179.2g in 100 g H2O at 0OC

Degree of Solubility g per 100g H2O at a given
temp
11
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12
What factors affect how soluble something is
  • How hot the solvent is
  • Polarity, How easy a block of substance is
    broken by the solvent or goes into solution
  • The surface area of the solute

13
Solubility curve
14
Solubility of sugar in water
15
Saturate room temperature water with sugar
16
So as the heat goes up then more solute can be
carried by the solvent
Super saturate the solvent (water) with solute
(sugar)
  • On the other hand the less heat the less ability
    the solvent has to carry the solute

17
As the sugar water solution cools down, what
happens to the sugar?
  • The solvent can no longer hold the solute and the
    solute falls out of solution and globs

18
So Hot liquids hold more soluteHot liquids hold
less gas
  • Rock candy

19
  • Unsaturated
  • Supersaturated
  • saturated

Identify the areas that are unsaturatedsupersatu
ratedsaturated
20
Who has ever used HEAT product in their gas to
keep water out
  • Gasoline freezes at 70 Fahrenheit

21
Gases have strange solubility properties Gases
dont glob
  • Gases are free moving unencumbered molecules
  • Gases do not become assimilated by the solvent
    but move into the spaces between solvent molecule
    because there is room and they happen to be
    floating by

22
Gasesare notassimilatedby the solvent
23
A solvent is saturated by a gas when the number
of gas molecules floating in equals the number of
gas molecules floating out
  • Kind of like kids moving in and out of a store in
    the mall

Equilibrium
24
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25
You can force more gas into a solvent with
pressurePressure is adding more atoms by adding
more atoms to the surface of a solution
  • Take the pressure off and the gas will leave the
    solution

26
Henrys Law
  • the solubility of a gas increases as
  • the partial pressure of the gas on the surface of
    the liquid increases.

The more atoms or molecules of a gas striking the
surface of a liquid the more gas will go into
solution
27
Pressure of the gas over the liquid
Higher pressure greater concentration of gas on
surface so greater number of gas molecules
entering water
28
Which do you think holds more gas, Hot water or
cold water?
  • Hot Water molecules heat the gaseous molecules
    causing them to move very rapidly and move far
    apart. Therefore less gas molecules will fit in
    the water.
  • Cold Water allows the gas already in the water
    to move slowly and stay more condensed in
    solution in greater amounts.

29
When you see dead fish on a small lake is it
because the fish got too hot?
Not enough oxygen dissolved in the water
30
When you see dead fish on a small lake is it
because the fish got too hot?
Not enough oxygen dissolved in the water
31
  • Which will explode with more fervor, opening a
    warm coke or a cold coke, Why?

32
An electrolyte is a substance that dissolves in a
liquid solvent and provides ions that conduct
electricity.
33
In order for an electrolyte to carry an electric
current there must be available charges for the
electron to jump to
34
Electrolytes are considered as
  • Strong electrolytes completely dissociate into
    ions and conduct electricity well.
  • Weak electrolytes provide few ions in solution.

35
When we did the electrolysis of water we had to
put acid in the water so the water would carry a
current
How does acid cause water to ionize?
36
An acid is an unstable molecule that shoots a
hydrogen atom without an electron loose
  • These protons (H) stick to any negative pole
    that is around and create positive ions

37
H2O H ? H3O hydronium
  • It is hydronium that allows water to carry a
    current.
  • Water can also carry a current if NaCl is added
    to the water. Na is the part that can carry a
    current, not Cl-

38

But how does the presence of a solute effect the
properties of the solvent.
  • Colligative Properties

39
We all know that when it gets very cold outside
we put salt on the roads to interfere with the
freezing of water.
  • WHY????????

40
Normally water freezes at O degrees
  • If we add salt to the water the Na and the Cl-
    interfere with the hydrogen bonding of the water
    molecules and prevents the crystallization of
    water.
  • Thus salt water freezes not at O degrees but
  • 20 degrees C (-4 F).

41
Pile of tires and box story
42
But is there something especially magical about
salt. What is so special about salt.
  • Will
  • sugar
  • KBr
  • MgCl2
  • Oil

43
Sugar, calcium chloride, almost any polar
substance that would interfere with the
electrostatic attraction of the hydrogen bonds of
the water will decrease the freezing temperature.
  • The extent that a polar compound changes the
    freezing point is called the
  • Freezing point depression

44
Do you think NaCl influences the freezing point
depression to the same degree as MgCl2?
45
The addition of a polar substance into water not
only decreases the freezing temperature, it also
changes the boiling point 
46
Water boils by individual H2O molecules breaking
loose from the hydrogen bonds of liquid water
  • The presence of a solute in the water acts as a
    barrier to the gas from escaping form the water.

Kind of like placing a turnstile in front of the
entrance into a auditorium
47
In this monument it would be easy for a group of
people to enter or leave from the building
48
If however a red turnstile is placed in the
doorways then the flow of people will be
disrupted and more energy will be needed for the
people to exit
49
The solute interferes with the escape of gaseous
water so you need to add more heat to achieve
boiling temperature
50
The change that a solute in a solution makes to
the boiling point is called the Boiling point
elevation
  • Stack of tires and a few pesky boxes
  • Trying to get out of the water when there are
    float toys in the water

51
My moms spaghetti
  • What examples can you think of
  • other than salt
  • that is an example of Colligative properties
    where there is freezing point depression and and
    boiling point elevation?

52
Antifreeze
  • Ethylene glycol

53
what do they say about pets and ethylene glycol
sugar
Anti-freeze
54
Do you think all substances lower the freezing
point and raise the boiling point the same
amount???? 
  • No

55
Aqueous means in water
Boiling and Freezing point changes for some
aqueous solutions
56
It is the number of particles or ions or
molecules that influence the colligalitive
properties.
  • The mass of the particles is not a factor

57
There is an equation that allows us to calculate
the temp change
  • ?Tb kb x m Kb 0.51 for H2O
  • ?Tf kf x m Kf -1.86 for H2O

58
Review for the exam
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