The document summarizes key concepts about solutions from chapter 6, including: 1) It defines solutions, solutes, solvents, and aqueous solutions. 2) It describes general properties of solutions like transparency, electrolytes vs nonelectrolytes, and how volumes are non-additive. 3) It discusses concentration units like molarity, calculates concentrations from masses and volumes, and explains dilution. 4) It covers colligative properties like vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure that depend on solute concentration.

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Chapter 6
Solutions
Denniston
Topping
Caret
7th Edition

2. 6.1 Properties of Solutions
• Solution - homogeneous mixture
• Solute - the substance in the mixture present
in lesser quantity
• Solvent - the substance present in the largest
quantity
• Aqueous solution - solution where the
solvent is water
• Solutions can be liquids as well as solids and
gases

3. 6.1 Properties of Solutions Examples of Solutions
• Air - oxygen and several trace gases are
dissolved in the gaseous solvent, nitrogen
• Alloys - brass and other homogeneous
metal mixtures in the solid state
• Focus on liquid solutions as many important
chemical reactions take place in liquid
solutions

4. 6.1 Properties of Solutions General Properties of Liquid
Solutions
• Clear, transparent, no visible particles
• May have color
• Electrolytes are formed from solutes that are
soluble ionic compounds
• Nonelectrolytes do not dissociate
NaCl(s ) H→ Na + (aq ) + Cl- (aq )
2O
• Volumes of solute and solvent are not additive
– 1 L ethanol + 1 L water does not give 2 L of solution

5. 6.1 Properties of Solutions
Solutions and Colloids
• Colloidal suspension - contains solute
particles which are not uniformly
distributed
– Due to larger size of particles (1nm - 200 nm)
– Appears identical to solution from the
naked eye
– Smaller than 1 nm, have solution
– Larger than 1 nm, have a precipitate

6. 6.1 Properties of Solutions Degree of Solubility
• Solubility - how much of a particular solute can
dissolve in a certain solvent at a specified
temperature
• Factors which affect solubility:
1 Polarity of solute and solvent
• The more different they are, the lower the solubility
2 Temperature
• Increase in temperature usually increases solubility
3 Pressure
• Usually has no effect
• If solubility is of gas in liquid, directly proportional
to applied pressure

7. 6.1 Properties of Solutions Saturation
• Saturated solution - a solution that contains all the
solute that can be dissolved at a particular
temperature
• Supersaturated solution - contains more solute
than can be dissolved at the current temperature
• How is this done?
• Heat solvent, saturate it with solute then cool slowly
• Sometimes the excess will precipitate out
• If it doesn’t precipitate, the solution will be
supersaturated

8. 6.1 Properties of Solutions Solubility and Equilibrium
• If excess solute is added to a solvent, some
dissolves
• At first, rate of dissolution is large
• Later, reverse reaction – precipitation – occurs
more quickly
• When equilibrium is reached the rates of
dissolution and precipitation are equal, there is
some dissolved and some undissolved solute
• A saturated solution is an example of a dynamic
equilibrium

9. 6.1 Properties of Solutions Solubility of Gases: Henry’s Law
• Henry’s law – the number of moles of a gas
dissolved in a liquid at a given temperature is
proportional to the partial pressure of the gas
above the liquid
• Gas solubility in a liquid is directly proportional to
the pressure of the gas in the atmosphere in
contact with the liquid
• Gases are most soluble at low temperatures
• Solubility decreases significantly at higher
temperatures
– Carbonated beverages – CO2 solubility less when warm
– Respiration – facilitates O2 and CO2 exchange in lungs

10. 6.2 Concentration Based on Mass
6
• Concentration - amount of solute dissolved
in a given amount of solution
• Concentration of a solution has an effect on
– Physical properties
• Melting and boiling points
– Chemical properties
• Solution reactivity

11. 6.2 Concentration Based on
Weight/Volume Percent
• Amount of solute = mass of solute in grams
• Amount of solution = volume in milliliters
amount of solute
concentration =
Mass
amount of solution
• Express concentration as a percentage by
multiplying ratio by 100% = weight/volume
percent or % (W/V)
W grams of solute
% = ×100%
V milliliters of solution

12. 6.2 Concentration Based on Calculating Weight/Volume
Percent
Calculate the percent composition or % (W/V) of
2.00 x 102 mL containing 20.0 g sodium chloride
20.0 g NaCl, mass of solute
Mass
2.00 x 102 mL, total volume of solution
% (W/V) = 20.0g NaCl / 2.00 x 102 mL x 100%
= 10.0% (W/V) sodium chloride

13. Calculate Weight of Solute from
6.2 Concentration Based on
Weight/Volume Percent
Calculate the number of grams of glucose in
7.50 x 102 mL of a 15.0% solution
Mass
W grams of solute
% = × 100%
V milliliters of solution
15.0% (W/V) = Xg glucose/7.50 x 102 mL x 100%
Xg glucose x 100% = (15.0% W/V)(7.50 x 102 mL)
Xg glucose = 113 g glucose

14. 6.2 Concentration Based on Weight/Weight Percent
W grams solute
% = ×100%
W grams solutions
• Weight/weight percent is most useful for
Mass
solutions of 2 solids whose masses are
easily obtained
• Calculate % (W/W) of platinum in gold
ring with 14.00 g Au and 4.500 g Pt
[4.500 g Pt / (4.500 g Pt + 14.00 g Au)] x 100%
= 4.500 g / 18.50 g x 100% = 24.32% Pt

15. 6.3 Concentration of Solutions:
Moles and Equivalents
• Chemical equations represent the relative
number of moles of reactants producing
products
• Many chemical reactions occur in solution
where it is most useful to represent
concentrations on a molar basis

16. 6.3 Moles and Equivalents Molarity
• The most common mole-based
concentration unit is molarity
• Molarity
– Symbolized M
– Defined as the number of moles of solute per
liter of solution
moles solute
M=
L solution

17. 6.3 Moles and Equivalents Calculating Molarity from Moles
• Calculate the molarity of 2.0 L of
solution containing 5.0 mol NaOH
• Use the equation moles solute
M=
L solution
• Substitute into the equation:
MNaOH = 5.0 mol solute
2.0 L solution
= 2.5 M

18. 6.3 Moles and Equivalents Calculating Molarity From Mass
• If 5.00 g glucose are dissolved in 1.00 x 102 mL of
solution, calculate molarity, M, of the glucose solution
• Convert from g glucose to moles glucose
– Molar mass of glucose = 1.80 x 102 g/mol
5.00 g x 1 mol / 1.80 x 102 g = 2.78 x 10-2 mol glucose
– Convert volume from mL to L
1.00 x 102 mL x 1 L / 103 mL = 1.00 x 10-1 L
• Substitute into the equation:
moles solute
M=
L solution
Mglucose = 2.78 x 10-2 mol glucose
1.00 x 10-1 L solution
= 2.78 x 10-1 M

19. 6.3 Moles and Equivalents Dilution
Dilution is required to prepare a less
concentrated solution from a more
concentrated one
– M1 = molarity of solution before dilution
– M2 = molarity of solution after dilution
– V1 = volume of solution before dilution
– V2 = volume of solution after dilution
moles solute
M= moles solute = (M)(L solution)
L solution

20. 6.3 Moles and Equivalents Dilution
• In a dilution will the
number of moles of solute
change?
– No, only fewer per unit
volume
• So, M1V1 = M2V2
• Knowing any three terms
permits calculation of the
fourth

21. 6.3 Moles and Equivalents Calculating Molarity
After Dilution
• Calculate the molarity of a solution made by
diluting 0.050 L of 0.10 M HCl solution to a
volume of 1.0 L
– M1 = 0.10 M molarity of solution before dilution
– M2 = X M molarity of solution after dilution
– V1 = 0.050 L volume of solution before dilution
– V2 = 1.0 L volume of solution after dilution
• Use dilution expression M1V1 = M2V2
• X M = (0.10 M) (0.050 L) / (1.0 L)
0.0050 M HCl OR 5.0 x 10-3 M HCl

22. 6.3 Moles and Equivalents Representation of Concentration
of Ions in Solution
Two common ways of expressing
concentration of ions in solution:
1. Moles per liter (molarity)
• Molarity emphasizes the number of
individual ions
2. Equivalents per liter (eq/L)
• Emphasis on charge

23. 6.3 Moles and Equivalents Comparison of Molarity and
Equivalents
1 M Na3PO4
• What would the concentration of PO43- ions be?
• 1M
• Equivalent is defined by the charge
• One Equivalent of an ion is the number of grams
of the ion corresponding to Avogadro’s number of
electrical charges
molar mass of ion (g)
One equivalent of an ion =
number of charges on ion

24. 6.3 Moles and Equivalents Molarity vs. Equivalents – 1 M Na3PO4
• 1 mol Na+ = 1 equivalent Na+
• 1 mol PO43- = 3 equivalents PO43-
• Equivalents of Na+?
– 3 mol Na+ = 3 equivalents of Na+
• Equivalents of PO43-?
– 1 mol PO43- = 3 equivalents of PO43-

25. 6.3 Moles and Equivalents Calculating Ion Concentration
• Calculate eq/L of phosphate ion, PO43- in a
solution with 5.0 x 10-3 M phosphate
• Need to use two conversion factors:
– mol PO43- mol charge
– mol charge eq PO43
5.0 x 10-3 mol PO43- x 3 mol charge x 1 eq
1L 1 mol PO43- 1mol charge
• 1.5 x 10-2 eq PO43- /L

26. 6.4 Concentration-Dependent
Solution Properties
• Colligative properties - properties of
solutions that depend on the concentration
of the solute particles, rather than the
identity of the solute
• Four colligative properties of solutions
1. vapor pressure lowering
2. boiling point elevation
3. freezing point depression
4. osmotic pressure

27. 6.4 Concentration-Dependent Vapor Pressure of a Liquid
Consider Raoult’s law in molecular
Solution Properties
terms
• Vapor pressure of a solution
results from escape of solvent
molecules from liquid to gas
phase
• Partial pressure of gas phase
solvent molecules increases
until equilibrium vapor
pressure is reached
• Presence of solute molecules
hinders escape of solvent
molecules, lowering
equilibrium vapor pressure

28. 6.4 Concentration-Dependent Vapor Pressure Lowering
• Raoult’s law - when a nonvolatile solute is
Solution Properties
added to a solvent, vapor pressure of the solvent
decreases in proportion to the concentration of
the solute
• Solute molecules (red below) serve as a barrier to
the escape of solvent molecules resulting in a
decrease in the vapor pressure

29. 6.4 Concentration-Dependent Freezing Point Depression and
Solution Properties Boiling Point Elevation
• Freezing point depression may be explained
considering the equilibrium between solid and
liquid states
– Solute molecules interfere with the rate at which
liquid water molecules associate to form the solid
state
• Boiling point elevation can be explained
considering the definition as the temperature at
which vapor pressure of the liquid equals the
atmospheric pressure
– If a solute is present, then the increase in boiling
temperature is necessary to raise the vapor pressure
to atmospheric temperature

30. 6.4 Concentration-Dependent Freezing Point Depression
• Freezing point depression (∆Tf) - is proportional
Solution Properties
to the number of solute particles
– Solute particles, not just solute
• How does an electrolyte behave?
– Dissociate into ions
• An equal concentration of NaCl will affect the
freezing point twice as much as glucose (a
nonelectrolyte)
• Each solvent has a unique freezing point
depression constant or proportionality factor
∆Tf=kf m

31. 6.4 Concentration-Dependent Boiling point elevation
• Boiling point elevation (∆Tb) - is
Solution Properties
proportional to the number of solute
particles
• An electrolyte will affect boiling point to
a greater degree than a nonelectrolyte of
the same concentration
• Each solvent has a unique boiling point
elevation constant
∆Tb=kb m

32. 6.4 Concentration-Dependent Osmotic Pressure
• Some types of membranes appear impervious
Solution Properties
to matter, but actually have a network of small
holes called pores
• These pores may be large enough to permit
small solvent molecules to move from one side
of the membrane to the other
• Solute molecules cannot cross the membrane as
they are too large
• Semipermeable membrane - allows
solvent but not solute to diffuse from one side
to another

33. 6.4 Concentration-Dependent
Osmotic Pressure
• Osmosis - the
Solution Properties
movement of
solvent from a
dilute solution to a
more concentrated
solution through a
semipermeable
membrane
• Requires pressure
to stop this flow

34. 6.4 Concentration-Dependent Osmotic Pressure
Solution Properties
• Osmotic pressure (π) - the amount of
pressure required to stop the flow across
a semipermeable membrane
π=MRT
• Osmolarity - the molarity of particles in
solution
– Osmol, used for osmotic pressure
calculation

35. 6.4 Concentration-Dependent Tonicity and the Cell
• Living cells contain aqueous solution and these cells
Solution Properties
are also surrounded by aqueous solution
• Cell function requires maintenance of the same osmotic
pressure inside and outside the cell
• Solute concentration of fluid surrounding cells higher
than inside results in a hypertonic solution causing
water to flow into the surroundings, causing collapse =
crenation
• Solute concentration of fluid surrounding cells too low,
results in a hypotonic solution causing water to flow
into the cell, causing rupture = hemolysis
• Isotonic solutions have identical osmotic pressures and
no osmotic pressure difference across the cell
membrane

36. 6.4 Concentration-Dependent Tonicity and the Cell
Solution Properties
Crenation Hemolysis Isotonic

37. 6.4 Concentration-Dependent Pickling Cucumber in Hypertonic
Solution Properties Brine Due to Osmosis

38. 6.5 Water as a Solvent
• Water is often referred to as the “universal
solvent”
• Excellent solvent for polar molecules
• Most abundant liquid on earth
• 60% of the human body is water
– transports ions, nutrients, and waste into and out of
cells
– solvent for biochemical reactions in cells and
digestive tract
– reactant or product in some biochemical processes