Chap. 12
Physical Properties of Solutions

•    Solution:  homogenous mixture

•           Types of Solutions

•                   Table 12.1   p. 468

•    Focus on where we have one liquid component

•         Have looked at aqueous(aq)

•             Ionic salt dissolved in H2O

Solution= Solute + Solvent

•    Focus on gas-liquid, liquid-liquid

•                    solid-liquid

•    Saturated:  contains the maximum amount of solute that will dissolve in a given amount of solute at a given temperature.  Tabled values called solubilities

•    LIKE DISSOLVES LIKE

 

•    Unsaturated:  more solute will dissolve

•    Supersaturated:  contains more solute, is unstable

•    Crystallization=precipitation

•        seeding out

Solubility

•    Miscible:  completely soluble

•    Solvation:  ion or molecule is surrounded by solvent molecules arranged in a specific manner;  called hydration if solvent is water

•    Table 4.2, p109:  Solubility rules

Predict the solubilities
Why?

•    A.  H2O(l) and C2H5OH(l)

 

•      B.  O2(g) and SO2(g)

 

•    C.  HCl(g) and H2O(l) 

 

•    D.  H2O2(l) and NaCl(s)

 

A.  Arrange in order of increasing solubility in H2O(l)

•      HBr,  LiF,  CO2,  CH3COOH

 

•      B.  Increasing solubility in C6H6(l)

•            Br2, SO2, CH4, CH3OH

Concentration units

•    Quantitative Study

•       amount of solute in a given amount of solution

 

•    Solution = solute + solution

Molarity = M

•                         moles of solute

                Liters of solution

 

Review sect. 4.5

•           Of a compound

•            of the ions in solution

 

Molality = m

•                     moles of solute

•                     kg of solvent

 

•    A.  Of the compound

•    B.  Of the ions in solution

You have dissolved 46.7 g NaBr in 125.6 g of water.  The density of the solution is 1.103 g/mL.

•    A.  What is the Molarity of the solution? 

•    B.  What is the Molarity of the ions in solution?

•    C.  What is the molality of the solution?

•    D.  What is the molality of the ions in solution?

You have dissolved 128.8 g Zinc nitrate in 975 mL of water. Density of the solution = 1.107 g/mL

•    A.  What is the Molarity of the solution? 

•    B.  What is the Molarity of the ions in solution?

•    C.  What is the molality of the solution?

•    D.  What is the molality of the ions in solution?

% by mass (weight)

•    This is % by mass of solute

•    % = part/whole                 so

•              

•                 mass of solute     x 100

                mass of solution

 

Or grams solute/100 grams solution

% by volume

•                   volume solute x 100

•                   volume solution

 

•      or      mL solute/100ml solution

Mole fraction = x

•    Introduced in sect. 5.6

 

•         Xamoles of component a

•                  total # moles

 

•    Mole % = mole fraction x 100

Parts per million = ppm

•                   mg solute

•                   Liter of H2O

 

•    Used in water testing

Density = d

•    Is specific for the compound or the solution.

 

•      d = g/mL         solids and liquids

 

•      d = g/L            gas

 

•    PAY ATTENTION TO UNITS

You have dissolved 45.7 g magnesium phosphate in enough water to create 150.0 mL of solution.

•    A.  Molarity of the solution?

•    B.  Molar conc. Of the ions?

•    C.  Molality of the solution?

•    D.  Molality of the ions?

•    E. % by mass?

•    F.  Mole fraction of solute?

•    G.  Ppm?

A 4.03 M C2H4(OH)2 solution has a density of 1.045 g/mL.

•    A.  What is the molality?

•    B.  What is the ppm?

•    C.  What is the % by mass?

•    D.  What is the mole fraction?

You have dissolved 36.7 mL CH4 (d=0.528g/mL) in 125 g C6H6 (d=0.627g/mL)

•    A.  What is the Molarity?

•    B.  What is the molality?

•    C.  % by mass?

•    D.  % by volume?

•    E.  Mole fraction?

Concentrated Sulfuric acid is 95.0% by mass with a density o 1.84 g/mL.

•    A.  What is the Molarity?

•    B.  What is the Molality?

A 10.7 m NaOH solution has a density of 1.33 g/mL.

•    A.  What is the Molarity?

•    B.  What is the % by mass?

 

 

 

•    OTHERS!!

Effect of Temperature on Solubility

•    Solids:  generally solubility increases with the increase in temperature.

•   
Fractional crystallization:  separate by temperature

 

Gas Solubility

•    In water, solubility decreases with increase in temperature

 

C = kP

•    C = solubility of the gas in solution

•    K = proportionality constant

•             This is temp. dependent

•    P = pressure of the gas above the solution

Colligative Properties

•    Vapor Pressure Lowering

 

•    Boiling Point Elevation

 

•    Freezing point Depression

 

•    Osmotic Pressure

Colligative properties of nonelectrolytes

•    Depends only on the number of solute particles in solution, not on the identity.  The particles can either be ions, atoms, or molecules.  Solute is nonvolatile.  Good for <0.2M

•    Table 12.2, p. 485

 

 

 

Freezing point depression

•     change in temp. = kfm

 

•    Kf = molal freezing point depression constant,  reflects the size of the magnitude

   m = molality

Tsoln(f.p)= Tpure(f.p) - change            

     

Boiling point elevation

•    Change in temp. = kbm

 

•    Kb = molal boiling point constant

 

•    Tsoln(b.p) = Tpure(b.p) + change

Nonvolatile solute!!

•    1.  What is the boiling point and freezing point of a solution containing 140.0 g C12H22O11 in 400.0 g of water?

•    2.  What is the boiling point and freezing point of a solution that contains 26.4 g C6H4Br2 dissolved in 0.250 kg C6H6?

 

•    3.  How many grams of C8H18 is dissolved in 455.0 g cyclohexane if the freezing point of the solution is –1.5oC?

•    4.  How many grams of carbon dioxide will raise the boiling point of 125 g acetic acid by 2.6oC?

 

•    5.  A sample containing 1.350 g of a nonelectrolyte lowered the freezing point of 10.0 g benzene by 3.66oC.  Calculate the molar mass of the nonelectrolyte.

 

•    6.  A 384 g nonelectrolyte compound, which has the empirical formula of C4H2N, dissolved in 500.0 g benzene lowers the freezing point to 5.19oC.  What is the Molecular formula of this compound?

 

•    7.  A solution containing 1.00 g of an unknown nonelectrolyte, containing 80.78%C, 13.56%H, and 5.66%O, dissolved in 8.50 g benzene has a freezing point of 3.37oC.  What is the molecular formula of the compound?

Containing an electrolyte

•    Electrolytes (ionic compounds) disociate when ina solution.  Colligative properties depend on the number of solute particles.  So,

100%ionization

•    Change in temp. = kmions

 

•    What is the freezing point and boiling point of a solution that contains 27.9 g calcium chloride dissolved in 125.6 mL of water?

Less than 100%ionization

•    Van’t Hoff factor = I

•    Given

•    Have ion pairs:  anion and cation are held together by electrostatic attraction and act like only one particle.

•    Table 12.3, p. 492

 

•    Change in temp. = ikmcompound

 

•    What is the boiling point and freezing point o a solution that contains 25.0 g MgSO4 dissolved in 100.0 g water, where I= 1.3?

Vapor Pressure lowering

•    Nonvolatile solute, volatile solvent

•    Looking at vapor pressure of the solvent above the solution.

 

•      P = xsolventPo

 

 

•    You have dissolved 5.00 g urea (MM = 60.856 g/mole) in 100.0 g water at a temp. of 27oC.  Pure water has a vapor pressure of 23.7 mmHg at 27oC.  What is the vapor pressure above the solution?

Osmotic Pressure

•    Pressure required to stop osmosis.

•    Osmosis:  the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated.

•        ρ = MRT

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