ii iii i c. johannesson i. the nature of solutions ch. 14 - solutions
TRANSCRIPT
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II
III
I
C. Johannesson
I. The Nature of SolutionsI. The Nature of Solutions
Ch. 14 - SolutionsCh. 14 - Solutions
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C. Johannesson
Definitions Definitions
Solution - Solution - homogeneous mixture
Solvent Solvent - present in greater amount
Solute Solute - substance being dissolved
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C. Johannesson
Definitions Definitions
Solute Solute - KMnO4 Solvent Solvent - H2O
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C. Johannesson
Solvation Solvation
Solvation – Solvation – the process of dissolving
solute particles are separated and pulled into solution
solute particles are surrounded by solvent particles
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C. Johannesson
SolvationSolvation
StrongElectrolyte
Non-Electrolyte
solute exists asions only
- +
salt
- +
sugar
solute exists asmolecules
only
- +
acetic acid
WeakElectrolyte
solute exists asions and
molecules DISSOCIATION IONIZATION
View animation online.
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C. Johannesson
Solvation Solvation
NONPOLAR
NONPOLAR
POLAR
POLAR
““Like Dissolves Like”Like Dissolves Like”““Like Dissolves Like”Like Dissolves Like”
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C. Johannesson
Solvation Solvation
Soap/DetergentSoap/Detergent• polar “head” with long nonpolar “tail”• dissolves nonpolar grease in polar water
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C. Johannesson
Solubility Solubility
SATURATED SOLUTION
no more solute dissolves
UNSATURATED SOLUTIONmore solute dissolves
SUPERSATURATED SOLUTION
becomes unstable, crystals form
concentration
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C. Johannesson
Solubility Solubility
SolubilitySolubility• maximum grams of solute that will
dissolve in 100 g of solvent at a given temperature
• varies with temp• based on a saturated soln
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C. Johannesson
Solubility Solubility
Solubility CurveSolubility Curve• shows the
dependence of solubility on temperature
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C. Johannesson
Solubility Solubility
Solids are more soluble at...Solids are more soluble at...• high temperatures.
Gases are more soluble at...Gases are more soluble at...• low temperatures &• high pressures
(Henry’s Law).• EX: nitrogen narcosis,
the “bends,” soda
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II
III
I
C. Johannesson
II. ConcentrationII. Concentration
Ch. 14 - SolutionsCh. 14 - Solutions
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C. Johannesson
ConcentrationConcentration
The amount of solute in a solution.
Describing Concentration
• % by mass - medicated creams
• % by volume - rubbing alcohol
• ppm, ppb - water contaminants
• molarity - used by chemists
• molality - used by chemists
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C. Johannesson
MolarityMolarity
Liters
moles(M)molarity
Must be in liters
1000 mL = 1 L L 1
mol0.25 0.25M
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C. Johannesson
MolalityMolality
solvent ofkg
solute of moles(m)molality
mass of solvent only
1 kg water = 1 L waterkg 1
mol0.25 0.25m
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C. Johannesson
2211 VMVM
Dilution Dilution
Preparation of a desired solution by adding water to a concentrate.
Moles of solute remain the same.
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C. Johannesson
Preparing Solutions Preparing Solutions
500 mL of 1.54M NaCl
500 mLwater
45.0 gNaCl
• mass 45.0 g of NaCl• add water until total
volume is 500 mL• mass 45.0 g of NaCl• add 0.500 kg of water
500 mLmark
500 mLvolumetric
flask
1.54m NaCl in 0.500 kg of water
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C. Johannesson
Preparing Solutions Preparing Solutions
Copyright © 1995-1996 NT Curriculum Project, UW-Madison(above: “Filling the volumetric flask”)
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C. Johannesson
Preparing Solutions Preparing Solutions
Copyright © 1995-1996 NT Curriculum Project, UW-Madison(above: “Using your hand as a stopper”)
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C. Johannesson
Preparing Solutions Preparing Solutions
250 mL of 6.0M HNO3 by dilution
• measure 95 mL of 15.8M HNO3
95 mL of15.8M HNO3
water for
safety
250 mL mark
• combine with water until total volume is 250 mL
• Safety: “Do as you oughtta, add the acid to the watta!”
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C. Johannesson
Solution Preparation LabSolution Preparation Lab
Turn in one paper per team. Complete the following steps:
A) Show the necessary calculations.
B) Write out directions for preparing the solution.
C) Prepare the solution. For each of the following solutions:
1) 100.0 mL of 0.50M NaCl
2) 0.25m NaCl in 100.0 mL of water
3) 100.0 mL of 3.0M HCl from 12.1M concentrate.
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II
III
I
C. Johannesson
III. Colligative Properties
III. Colligative Properties
Ch. 14 - SolutionsCh. 14 - Solutions
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C. Johannesson
Definition Definition
Colligative PropertyColligative Property
• property that depends on the
concentration of solute particles, not
their identity
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C. Johannesson
Types Types
Freezing Point DepressionFreezing Point Depression (tf)
• f.p. of a solution is lower than f.p. of the pure solvent
Boiling Point ElevationBoiling Point Elevation (tb)
• b.p. of a solution is higher than b.p. of the pure solvent
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C. Johannesson
Types Types
View Flash animation.
Freezing Point Depression
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C. Johannesson
Types Types
Solute particles weaken IMF in the solvent.
Boiling Point Elevation
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C. Johannesson
Types Types
Applications• salting icy roads• making ice cream• antifreeze
• cars (-64°C to 136°C)• fish & insects
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C. Johannesson
Calculations Calculations
t: change in temperature (°C)
k: constant based on the solvent (°C·kg/mol)
m: molality (m)
n:# of particles
t = k · m · n
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C. Johannesson
Calculations Calculations
# of Particles# of Particles
• Nonelectrolytes (covalent)• remain intact when dissolved • 1 particle
• Electrolytes (ionic)• dissociate into ions when dissolved• 2 or more particles
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C. Johannesson
Calculations Calculations
At what temperature will a solution that is composed of 0.73 moles of glucose in 225 g of phenol boil?
m = 3.2mn = 1tb = kb · m · n
WORK:
m = 0.73mol ÷ 0.225kg
GIVEN:b.p. = ?tb = ?
kb = 3.60°C·kg/moltb = (3.60°C·kg/mol)(3.2m)(1)
tb = 12°C
b.p. = 181.8°C + 12°C
b.p. = 194°C
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C. Johannesson
Calculations Calculations
Find the freezing point of a saturated solution of NaCl containing 28 g NaCl in 100. mL water.
m = 4.8m
n = 2
tf = kf · m · n
WORK:
m = 0.48mol ÷ 0.100kg
GIVEN:
f.p. = ?
tf = ?
kf = 1.86°C·kg/mol
tf = (1.86°C·kg/mol)(4.8m)(2)
tf = 18°C
f.p. = 0.00°C - 18°C
f.p. = -18°C