It’s Friday! Air Bag Testing You need out your air bag lab from yesterday. Continue working with your partner on the calculations. You have 20 minutes to calculate AND test (you have two trials) your simulation air bag. Vocabulary Slides: http:// goo.gl/eju5D1
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It’s Friday! Air Bag Testing You need out your air bag lab from yesterday. Continue working with your partner on the calculations. You have 20 minutes.
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It’s Friday! Air Bag Testing
You need out your air bag lab from yesterday. Continue working with your partner on the
calculations. You have 20 minutes to calculate AND test (you have two trials) your simulation
Soluble SaltsCOMPOUNDS OF THESE IONS ARE ALWAYS SOLUBLE
EXCEPT WITH
NO3-, Group I, NH4
+, C2H3O2-, ClO4
-, ClO3
-
No exceptions
Cl-, Br-, I- Pb+2, Ag+1, Hg2+2
SO4-2 Pb+2, Ag+, Hg2
+2, Ca+2, Sr+2, Ba+2
•If a compound does not fit into one of the three categories above, assume it is insoluble and a nonelectrolyte (fix this in your notes).
•Also – gases, pure liquids, and solids are nonelectrolytes. (but gases can be dissolved in water)
SolubilitySATURATED SOLUTIONno more solute dissolves
UNSATURATED SOLUTIONmore solute dissolves
SUPERSATURATED SOLUTIONbecomes unstable, crystals form
concentration
Saturated Solution:
Saturation of a solution is sort of like saturation of a sponge. There are only so many holes in a sponge to hold a liquid, and when it is full there is simply no more room.
Magnified Sponge (x40)
Unsaturated Solution An unsaturated solution
is like a sponge that can hold more water.
More solute can be dissolved at that temperature.
I’m still thirsty!
Supersaturated Solution
Can be prepared by
changing the conditions
of a saturated solution
(temperature, volume,
or pressure).
A supersaturated solution is a solution that contains more of the solute than it can normally hold.
How is Solubility Expressed?
_____ g / 100g of water at ____ °C
Solvent Temperature
Solubility is the amount of a substance that can be dissolved in a liquid under specified conditions.
Solute
How is Solubility Expressed?
_____ g / 100g of water at ___ °C
Control Independent Variable
(CAUSE)
Dependent Variable
(EFFECT)
SolubilityEx: 80 grams of KNO3 will dissolve in 100 grams of water at 50 degrees Celsius.
This is the maximum amount.
Called “saturation”
SolubilityUnsaturated is when more solute could dissolve.
Ex: 70 grams of KNO3 dissolved in 100 grams of water at 60 degrees Celsius.
Any point below the line is unsaturated. You could dissolve more.
SolubilitySupersaturated is when more is dissolved than normally could be.
Ex: 110 grams of KNO3 dissolved in 100 grams of water at 60 degrees.
Any disturbance or seed crystal will cause the excess to precipitate out.
How much will ppt out in this situation?
Review What We’ve Learned
Solutions that are described by the line are always SATURATED SOLUTIONS.
Solutions that are above the line are always SUPERSATURATED SOLUTIONS.
Solutions that are below the line are always UNSATURATED SOLUTIONS.
Practice
How much KClO3 could possibly dissolve at 70 oC?
Which compound is least soluble at 40 oC?
How many grams of NaCl could dissolve at 10 oC?
Practice
90 grams of sodium nitrate is dissolved in 100 grams of water at 30 oC. The solution is ____.
Which substance is least soluble at 0 oC?
Solubility Trends Seen..
Solids become more soluble as temperature increases.
Gases become less soluble as temperature increases.
Solubility Curve:____ g / 100g of water at
____ °C
What if we change the amount of water?
Think About It:If we make one pack of Kool-Aid, we will need 2 quarts of water.
If we make two packs of Kool-Aid, and we want it to have the same concentration as a 1 pack Kool-Aid solution, how much water would we need?
Solubility CurveIn order to reach saturation, if we double the amount of water that is being used to prepare the solution, we would need to also double the solute.
20 g / 100g of water at 25 °C
40 g / 200g of water at 25 °C
How many grams of ammonia could dissolve in 200 grams of water at 50 oC?
If 95 grams of NaCl is dissolved in 200 grams of water at 90 oC, is the solution saturated, unsat, or supersat?
Measuring the Concentration of
Solutions
MolarityThe molarity of a solution is a measure of how many moles of solute are present for each liter of solution. The higher the molarity, the more concentrated a solution is.
Molarity (M) = mol solute
L solution
Molarity is useful in stoichiometric problems.
Molality – another measure of concentration
Molality is the concentration of a solution calculated by dividing the number of moles of solute by kilograms of solvent (usually water) used to dissolve.
m = mol solute
kg solvent
This measurement is useful for something else – calculating how boiling and freezing temperatures changes as you add solute to solvent.
Mole Fractionanother measure of
concentration
Say you have a solution made of component 1 and component 2
Mole fraction for component 1 of solution = moles of component 1
total moles of all components
In other words:
X = 1
1+2 THIS IS A FRACTION SO THERE ARE NO UNITS
Percent MassThe last measure of concentration!
% mass = grams component x 100
grams of mixture
DilutionsFrequently it is necessary to dilute a more concentrated solution to produce the needed concentration in the lab.
I may have 18 molar sulfuric acid, but I need only a small amount of 1 molar.
Dilutions FormulaM1V1 = M2V2
M is molarity
V is volume
1 is initial (higher concentration)
2 is final (diluted concentration)
Colligative Properties of Solutions
Colligative Properties
Properties of a solution that depend on the amount of solute particles the type of particle doesn’t matter.
Freezing Point Depression
By adding a nonvolatile solute, we can change a solvent’s freezing point and boiling point.
Nonvolatile – doesn’t evaporate easily.
Freezing Point Depression
Antifreeze
Salt on iced over bridges
ΔT = Kfmi
ΔT = change in FP temperature
Kf = molal freezing point constant (-1.86 for water)
m = molality (mol solute / kg solvent)
i = number of ions
Boiling Point Elevation
Boiling point can be increased by adding a nonvolatile solution, and the “elevation” or number by which the BP is elevated, can be calculated.
Boiling Point Elevation
Cooking with boiling water
ΔT = Kbmi
ΔT = change in BP temperature
Kb = molal boiling point constant (0.51 for water)
m = molality (mol solute / kg solvent)
i = number of ions
If the solute is ionic & soluble.. It breaks into ions.
You have more particlesIf the solution has an ionic compound, it has more than one particle per formula unit.
Ex: MgCl2 (s) Mg+2 (aq) + 2Cl- (aq)
Three particles are present, so the change in temperature is tripled.
ΔTb = iKbm
ΔTf = iKfm
i = number of ions in the formula.
Vapor Pressure Lowering
The vapor pressure of a liquid is the pressure due to evaporated liquid in a closed container.
Decreasing Vapor Pressure
Adding a nonvolatile solute lowers the vapor pressure because surface area available for evaporation is limited.