AP Chapter 11 Notes Properties of Solutions
Most substances in our world are solutions. To discuss, we must be able to quantitatively using the following concentrations:
Molarity = .
Mass % = .
Molality = .
Mole Fraction = .
Normality = .
Ex. 11.1 page 514
A solution is prepared by mixing 1.00 g ethanol (C2H5OH) with 100.0 g water to give a final volume of 101 mL. Calculate the molarity, mass percent, mole fraction and molality of ethanol in this solution.
More on Normality:
An equivalent depends on the type of reaction.
Acid/base reactions: an equivalent is the of acid or base that produce or accept 1 mole of .
Redox reactions: an equivalent is the of oxidizing or reducing agent that can accept or furnish 1 mole of .
MnO4- + 5 e- + 8 H+ ® Mn 2+ + 4 H2O
Ex 11.2 page 517
The electrolyte in automobile lead storage batteries is a 3.75 M sulfuric acid solution that has a density of 1.230 g/mL. Calculate the mass percent, molality, and normality of the sulfuric acid.
Dissolving involves the following steps:
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a) solutes which is a(n) step
b) overcoming which is a(n) step
c) allowing to interact which is a(n)
step
Enthalpy of solution, , is the sum of the above steps.
Enthalpy of hydration involves steps above.
Factors influencing solubility:
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tendency to or .
strength of .
processes requiring .
Ex 11.3 page 521
Decide whether liquid hexane (C6H14) or liquid methanol (CH3OH) is the more appropriate solvent for the substances grease (C20H42) and potassium iodide (KI).
Solubility is favored if and have similar or .
Pressure greatly affects solubility of .
Henry’s Law which is .
Henry’s Law
P = .
C = .
K = .
Henry’s law holds true for which do not dissociate or react with the solvent.
Ex 11.4 page 524
A certain soft drink is bottled so that a bottle at 25oC contains CO2 gas at a pressure of 5.0 atm over the liquid. Assuming that the partial pressure of CO2 in the atmosphere is 4.0 x 10-4 atm, calculate the equilibrium concentrations of CO2 in the soda both before and after the bottle is opened. The Henry’s Law constant for CO2 in aqueous solution is 32 L atm/mol at 25 oC.
Temperature affects dissolving:
dissolving usually occurs more with temperature
increases...The only way to know is through . Gases, on the other hand, usually dissolve as temperatures increase.
Vapor Pressure of Solutions
of a pure solvent are different with the addition of a solute. Some examples are .
Since addition of a solute the vapor pressure of a pure solvent, the new vapor pressure can be calculated using Raoult’s Law:
Ex 11.5 page 529
Calculate the expected vapor pressure at 25oC for a solution prepared by dissolving 158.0 g of common table sugar (sucrose, molar mass =342.3 g/mole) in 643.5 cm3 of water. At 25oC, the density of water is 0.9971 g/cm3 and the vapor pressure is 23.76 torr.
► In addition to a solute lowering the vapor pressure, a solute that dissociates must be considered since it adds to the number of moles of particles.
NaCl would actually provide moles of particles.
Ba(NO3)2 would provide moles of particles.
Ex 11.6 page 532
Predict the vapor pressure of a solution prepared by mixing 35.0 g solid Na2SO4 (molar mass=142 g/mol) with 175 g water at 25oC. The vapor pressure of pure water at 25oC is 23.76 torr.
Raoult’s Law must be modified when in liquid-liquid solutions both components are .
Ptotal = PA + PB = .
Negative Deviation occurs when solute-solvent attractions are . Positive Deviation occurs when solute-solvent attractions are .
Ex 11.7 page 535
A solution is prepared by mixing 5.81 g acetone (C3H6O, molar mass=58.1 g/mole) and 11.9 g chloroform (HCCl3, molar mass=119.4 g/mol). At 35oC, this solution has a total vapor pressure of 260. torr. Is this an ideal solution? The vapor pressures of pure acetone and pure chloroform at 35oC are 345 and 293 torr respectively.
Boiling Point Elevation and Freezing Point Depression
Since changes of state (solid to liquid to gas) depend on ,
the presence of a solute affects of a pure solvent.
Properties which are affected by the presence of a solute are called
Properties.
► Boiling Point elevation
normal boiling occurs when vapor pressure = .
Addition of a nonvolatile solute vapor pressure, thus the solution must be heated more in order for boiling to occur. We calculate the change in the boiling point by:
rTb =
Ex 11.8 page 537
A solution was prepared by dissolving 18.00 g glucose in 150.0 g water. The resulting solution was found to have a boiling point of 100.34 oC. Calculate the molar mass of glucose. Glucose is a molecular solid that is present as individual molecules in solution.
► Freezing Point depression
normal freezing point occurs when vapor pressure of the solid and liquid are . With the addition of a nonvolatile solute, vapor pressure of the liquid is thus no solid forms until the temperature is lowered below the normal freezing point. We calculate the change in the freezing point by:
rTf =
Ex 11.9 page 538
What mass of ethylene glycol (C2H6O2, molar mass=62.1 g/mole), the main component of antifreeze, must be added to 10.0 L water to produce a solution for use in a car’s radiator that freezes at -10.0 oF (-23.3 oC)? Assume the density of water is exactly 1 g/mL.
Ex. 11.10 page 539
a chemist is trying to identify a human hormone, which controls metabolism, by determining its molar mass. A sample weighing 0.546 g was dissolved in 15.0 g benzene, and the freezing point depression was determined to be 0.240oC. Calculate the molar mass of the hormone.
Osmosis
A semi-permeable membrane separates a pure substance from its solution and allows .
Osmosis is the flow of into the until
occurs.
Osmotic Pressure
...is the pressure of the solution. Osmotic pressure depends on the solution concentrations shown as:
π =
Ex 11.11 page 541
To determine the molar mass of a certain protein, 1.00 x 10-3 g of it was dissolved in enough water to make 1.00 mL of solution. The osmotic pressure of this solution was found to be 1.12 torr at 25.0 oC. Calculate the molar mass of the protein.
Dialysis is a similar process. It allows the transfer of . and .
Ex 11.12 page 543
What concentration of sodium chloride in water is needed to produce an aqueous solution isotonic with blood (π = 7.7 atm at 25 oC)?
Reverse Osmosis
...occurs when a solution comes into contact with a . across a semi-permeable membrane and the external pressure is greater than the osmotic pressure. Then the membrane acts as a molecular filter to remove .
Colligative properties of electrolyte solutions
...depend upon the .
van’t Hoff Factor, i , shows the relationship
i = .
NaCl i =
K2SO4 i =
Fe3(PO4)2 i =
This assumes complete dissociation which is not true in very concentrated solutions....some ions will pair up, so we use the following to account for the variations:
rT =
or
π =
Ex 11.13 page 548
The observed osmotic pressure for a 0.10 M solution of Fe(NH4)2(SO4)2 at 25 oC is 10.8 atm. Compare the expected and experimental values for i.
Colloids
....are mixtures with relative particles suspended.
We can distinguish between colloids and solutions with the . which is conducted ....
What stabilizes a colloid?
Examples / Dispersing medium / Dispersed substance / Colloid typeFog, aerosol sprays / Gas / Liquid / Aerosol
Smoke, airborne bacteria / Gas / Solid / Aerosol
Whipped cream, soap suds / Liquid / Gas / Foam
Milk, mayonnaise / Liquid / Liquid / Emulsion
Paint, clays, gelatin / Liquid / Solid / Sol
Marshmallow, polystyrene foam / Solid / Gas / Solid foam
Butter, cheese / Solid / Liquid / Solid emulsion
Ruby glass / Solid / Solid / Solid sol
Assignment Chapter 11:
# 15, 16, 20, 24, 28, 31, 35, 39, 43, 47, 51, 55, 59, 64, 67, 72, 76
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