copyright©2000 by houghton mifflin company. all rights reserved. 1 chemistry properties of...
TRANSCRIPT
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
1
Chemistry
Properties of Solutions
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
2
What is one of the most important Substances on earth????????????
Water!!!!!!!!!!!!!!!!!!!!!
What is one of its most valuable properties?
Its ability to dissolve many different substances!!
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
3
Solutions
. . . the components of a mixture are uniformly intermingled (the mixture is homogeneous).
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
4
Solutions can be
• GasesEx. Air
• Solids
Ex. Brass
• LiquidsEx. Carbonated water
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
5
Focus
is
the properties of liquid solutions,particularly those containing water.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
6
Water, The Common SolventAqueous Solutions
Water is the dissolving medium, or solvent.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
7
•Figure 4.1
The Water Molecule is
· Polar
·Bent
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
8
Some Properties of Water Water is “bent” or V-shaped. The O-H bonds are covalent. Water is a polar molecule. Electrons are not equally shared. Unequal charge distribution.
O—H δ- δ+
Hydration occurs when salts dissolve in water.Polarity gives water ability to dissolve cpds.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
9
Polar Water Molecules Interact with the Positive and Negative Ions of a Salt
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
10
SOLUTION COMPOSITION
• SOLUTE - SUBSTANCE BEING DISSOLVED
• SOLVENT – DISSOLVING MEDIUM
• IF SOLID IN A LIQUID, THEN LIQUID IS SOLVENT
• IF LIQUID IN LIQUID, THE LIQUID OF LARGER AMOUNT IS SOLVENT.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
11
SOLUTION
• HOMOGENEOUS MIXTURE
• Solvent – Dissolving medium
• Solute – Substance dissolved
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
12
A Solute dissolves in water (or
other “solvent”)
changes phase (if different from the solvent)
is present in lesser amount (if the same phase as the solvent)
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
13
A Solvent
retains its phase (if different from the solute)
is present in greater amount (if the same phase as the solute)
• Solution - Solution - homogeneous mixture
Solvent Solvent – dissolving medium
Solute Solute - substance being dissolved
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
15
Factors Affecting how quickly solutions are formed
(Rate of solution formation)
• Stirring or agitation
• Particle size (grinding/crushing)
• Temperature
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
16
Solubility
• The amt of a solute that dissolves in a given amt of solvent at a specified temperature.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
17
Solubility
• Saturated solution-- Contains the max. amt of solute for a given amt of solvent at constant T & P (g solute/ 100 g solvent)
• Unsaturated solution-- Contains less than the max. amt of solute for a given amt of solvent at constant T & P
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
18
Solubility
• Supersaturated solution --Contains less than the max. amt of solute for a given amt of solvent at constant T & P
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
19
Factors Affecting Solubility
• STRUCTURE EFFECTS
-- “LIKE DISSOLVES LIKE”
-- SOLUBILITY IS FAVORED IF SOLUTE AND SOLVENT HAVE SIMILAR POLARITIES.
-- POLARITY DETERMINED BY MOLECULAR STRUCTURE
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
20
Solubility
• “LIKE DISSOLVES LIKE”
• Polar substances dissolve polar substances
• Nonpolar substances dissolve nonpolar substances
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
21
PRESSURE EFFECTS
• PRESSURE HAS
--- LITTLE EFFECT ON SOLUBILITY OF SOLIDS AND LIQUIDS
--- SIGNIFICANTLY INCREASES SOLUBILITY OF A GAS
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
22
Figure 11.5
A Gaseous Solute
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
23
Henry’s Law
P = kC
P = partial pressure of gaseous solute above the solution
C = concentration of dissolved gask = a constant
The amount of a gas dissolved in a solution is The amount of a gas dissolved in a solution is directly proportional to the pressure of the gas directly proportional to the pressure of the gas above the solution.above the solution.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
24
TEMPERATURE EFFECTS
• SOLUBILITY OF MOST SOLIDS IN WATER INCREASES WITH TEMPERATURE.
• SOLUBILITY OF SOME SOLIDS IN WATER DECREASE WITH TEMPERATURE.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
25
Figure 11.6
The Solubilities of Several Solids as a Function of Temperature
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
26
SOLUBILITY OF GASES IN WATER
• DECREASES WITH INCREASING TEMPERATURE.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
27
Figure 11.7
The Solubilities of Several Gases inWater
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
28
• The Composition of Solutions
Important to know the Amount of Chemicals present in a Solution.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
29
Solution Composition
1. Molarity (M) =
2. Mass (weight) percent =
3. Mole fraction (A) =
4. Molality (m) =
moles of soluteliters of solution
mass of solutemass of solution
100%
molestotal moles in solution
A
moles of solutekilograms of solvent
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
30
Molarity
Molarity (M) = moles of solute per volume of solution in liters:
M
M
molaritymoles of soluteliters of solution
HClmoles of HCl
liters of solution3
62
Molarity
• Concentration of a solution
solution of liters
solute of moles(M)Molarity
total combined volume
substance being dissolved
C. Molarity
2M HCl
L
molM
nsol' L 1
HCl mol 2HCl 2M
What does this mean?
C. Molarity Calculations
• How many grams of NaCl are required to make 0.500L of 0.25M NaCl?
0.500 L sol’n 0.25 mol NaCl
1 L sol’n
= 7.3 g NaCl
=.125 mol NaCl
58.44 g NaCl
1 mol NaCl
.125 mol NaCl
C. Molarity Calculations
• Find the molarity of a 250 mL solution containing 10.0 g of NaF.
10.0 g NaF 1 mol NaF
41.99 g NaF
L
molM .283 NaF
.25 L sol’n= 0.95 M
NaF
=.283 mol NaF
• Percent Composition by Mass
Mass of SoluteMass of Solution
x100
Percent by Mass
• How many moles of solute are contained in 343 grams of a 23% aqueous solution of MgCr2O7?
343g of solution 23%
100%
1 mol
240.3 g MgCr2O7
=0.329 mol of MgCr2O7
• Percent Composition by Volume
Volume of SoluteVolume of Solution
x100
B. Percent by Volume
• Determine the percent by volume of toluene (C6H5CH3) in a solution made by mixing 40.0 mL of toluene with 75.0 mL of benzene (C6H6).
40.0 mL toluene + 75.0 mL benzene= 115 mL total solution(40.0 mL toluene / 115 mL solution) 100 = 34.8%
toluene
Mole Fraction
Moles A
Total Moles= Mole Fraction, Χ
Molality
solvent ofkg
solute of moles(m)molality
mass of solvent only
1 kg water = 1 L waterkg 1
mol0.25 0.25m
D. Molality
• Find the molality of a solution containing 75 g of MgCl2 in 250 mL of water.
75 g MgCl2 1 mol MgCl2
95.21 g MgCl2
= 3.2m MgCl2
0.25 kg water
kg
molm
D. Molality
• How many grams of NaCl are req’d to make a 1.54m solution using 0.500 kg of water?
0.500 kg water 1.54 mol NaCl
1 kg water
= 45.0 g NaCl
58.44 g NaCl
1 mol NaCl
kg 1
mol1.54 1.54m
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
43
Standard Solution
• Solution whose concentration is accurately known.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
44
Figure 4.10
Preparation of a Standard Solution
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
45
Dilution
• Solutions are often prepared by diluting more concentrated solutions.
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
46
Common Terms of Solution Concentration
Stock - routinely used solutions prepared in concentrated form.
Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl)
Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
47
“Solutions by Dilution”
• Moles of solute after dilution
EQUALS
Moles of solute before dilution
• M2 x V2 = M1 x V1
Dilution
• What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?
GIVEN:
M1 = 15.8M
V1 = ?
M2 = 6.0M
V2 = 250 mL
WORK:
M1 V1 = M2 V2
(15.8M) V1 = (6.0M)(250mL)
V1 = 95 mL of 15.8M HNO3
Copyright©2000 by Houghton Mifflin Company. All rights
reserved.
49
Figure 4.11(a) A Measuring Pipet (b) A Volumetric (transfer) Pipet