Types of mixtures Heterogeneous mixture: Heterogeneous mixtures
do not blend smoothly. Individual substances can still be seen
Suspension: A suspension is a heterogeneous mixture where particles
will settle to the bottom if left undisturbed. Example: sand in
water. Colloids: Colloids are heterogeneous mixtures where
particles will not settle to the bottom. Example: Milk
Slide 3
Homogeneous Mixtures Homogeneous mixtures are mixtures where a
substance is dissolved in another substance. These are also called
solutions. Parts of a solution: Solute: The substance that is
dissolved Solvent: The substance that does the dissolving When a
solute readily dissolves in a solvent it is said to be soluble. Two
liquids that can be combined to make a solution are said to be
miscible.
Slide 4
A solute that does not readily dissolve in a solvent is said to
be insoluble. Two liquids that do no mix to form a new solution are
said to be immiscible.
Slide 5
Solution Concentration Concentration is the measure of how much
solute is dissolved in the solution. There are many ways to measure
concentration Percent by mass: (Mass of solute/Mass of solution) x
100 Percent by volume: (Volume of solute/Volume of solution) x 100
Molarity: Moles of solute/Liter of solution Molality: Moles of
solute/Kilograms of solvent Mole Fraction: Moles of solute/Moles of
solute + Moles of solvent
Slide 6
Percent by mass In order to maintain a sodium chloride
concentration similar to ocean water, an aquarium must contain 3.6g
NaCl per 100.0 g of water. What is the percent by mass of NaCl in
the solution? 3.5% What is the percent by mass of NaHCO 3 in a
solution containing 20.0 g of NaHCO3 dissolved in 600.0 mL of H 2
O? 3%
Slide 7
Percent by Volume What is the percent by volume of ethanol in a
solution that contains 35mL of ethanol dissolved in 155mL of water?
18%
Slide 8
Molarity A 100.5 mL intravenous solution contains 5.10 g of
glucose. What is the molarity of the solution? The molar mass of
glucoes is 180.6 g/mol 0.282M
Slide 9
If you have 1500 g of a bleach solution with a percent by mass
of NaOCl of 3.62 % how many grams of NaCOl are in the solution?
54.3 g What is the percent by volume of isopropyl alcohol in a
solution that contains 24 mL of isopropyl alcohol in 1.1 L of
water? 2.1 % Calculate the molarity of 1.6 L of a solution
containing 1.55 g of KBr. 8.13 x 10 -3
Slide 10
Molality In the lab a student adds 4.5 g of NaCl to 100.0 g of
water. Calculate the molaity of the solution. 0.77 mol/kg
Slide 11
Preparing Solutions How would you prepare 1 L of a 1.5 molar
CuSO 4 Solution? Diluting Solutions: Dilution equation M 1 V 1 = M
2 V 2 Calculate the new volume if you wanted to dilute the above
solution to 0.5 molar.
Slide 12
Diluting Solutions Remember Molarity = (Moles of solute/Liters
of solvent) The Dilution Equation: M 1 V 1 = M 2 V 2 Example: What
volume of a 2.00M CaCl 2 solution would you use to make 0.50 L of a
0.300M solution? M 1 = 2.00M V 1 = ? M 2 = 0.300M V 2 = 0.5L
(2.00M)(V 1 ) = (0.300M)(0.5L) V 1 = 0.075 L
Slide 13
What volume of a 3.00M KI solution would you use to make 0.300
L of a 1.25M KI solution? 125mL How many milliliters of a 5.0M H 2
SO 4 stock solution would you need to prepare 100.0mL of 0.25M H 2
SO 4 ? 5.0mL
Slide 14
Mole Fraction To express concentration as a mole fraction we
need to know the number of moles of solute and the number of moles
of solvent. The mole fraction is calculated by dividing the number
of moles of either the solute or solvent by the total number of
moles in the solution.
Slide 15
Example If we have a solution that contains 36 g of HCl and 64
g of H 2 O. What are the mole fractions of HCl and H 2 O? HCl: H 2
O:
Slide 16
Practice What is the mole fraction of NaOH in an aqueous
solution that contains 22.8% NaOH by mass? If the mole fraction of
H 2 SO 4 is an aqueous solution is 0.325, what is the percent by
mass of H 2 SO 4
Slide 17
Factors Affecting Solvation Many physical factors affect the
solubility of a solute. Such as: Temperature Pressure Polarity
Solvation is the process of surrounding solute particles with
solvent particles.
Slide 18
Aqueous ionic solutions Many ionic compounds are soluble in
water. Why? Water is a polar molecule. Why might an ionic compound
not be water soluble?
Slide 19
Heat of solution The overall energy change that occurs during
the formation of a solution is called the heat of solution. certain
solvation processes are exothermic while others are
endothermic.
Slide 20
Factors that affect solvation Agitation: Stirring or shaking
moves solvated particles away from the surface of the solid and
allows more solute particles to move into solution. Surface Area:
Breaking the solute into small pieces increases the available
surface area and increase the rate of solvation. Temperature: As
temperature increase so does the rate of solvation.
Slide 21
Types of solutions Unsaturated: A solution that more solute
could be dissolved in. Saturated: In a saturated solution the rate
of solvation and the rate of crystallization are in equilibrium.
Supersaturated solution: A super saturated solution is a solution
that has more solute dissolved in it that it would normally
allow.
Slide 22
Solubility of Gases Unlike solid solutes the solubility of
gases (CO 2, or O 2 for example) increases as the temperature of
the solvent goes down. The solubility of gases is also affected by
pressure. How? Think about soda.
Slide 23
Henrys Law Henrys Law states that at a constant temperature,
the solubility (S) of a gas in a liquid is directly proportional to
the pressure of the gas above the liquid. Henrys Law S 1 /P 1 = S 2
/P 2 Example: If 0.85g of a gas at 4.0 atm of pressure dissolves in
1.0 L of water at 25 o C, how much will dissolve in 1.0 L at 1.0
atm at the same temperature? 0.21 g
Slide 24
Decompression Sickness Decompression sickness is a term used to
describe the effects of a drop in external pressure on a persons
body. One common symptom of decompression sickness is AGE, Arterial
Gas Embolism. The bubbles that form in the blood stream from gas
leaving solution can restrict blood flow.
Slide 25
Slide 26
Boiling Point Elevation Dissolving a solute in a solution
raises the boiling point of the solution. This is called boiling
point elevation. We can calculate the difference in boiling point (
T b ) by multiplying a solutions molality by a constant we look up
for our particular solvent (K b ). T b = K b m
Slide 27
What is the boiling point of a 0.625m aqueous solution of a
nonelectrolyte?
Slide 28
What is the boiling point of a 0.4m aqueous solution of Ca(OH)
2 (A strong electrolyte) K b = 0.512 o C/m
Slide 29
Molal Boiling Point Elevation Constants. SolventBoiling Point (
o C)K b ( o C/m) Water100.00.512 Benzene80.12.53 Chloroform61.73.63
Ethanol78.51.22
Slide 30
Freezing Point Depression Adding a solute to a solvent also
lowers the solvents freezing point. The equation is very similar to
boiling point elevation. T f = K f m SolventFreezing Point ( o C) K
f ( o C/m) Water0.001.86 Benzene5.55.12 Ethanol-114.11.99
Slide 31
Example Sodium chloride is often used to prevent icy roads and
to freeze ice cream. What are the boiling point and freezing point
of a 0.029m AQUEOUS solution of sodium chloride? BP: 100.03 0 C FP:
-0.11 o C
Slide 32
Slide 33
Calculate the freezing and boiling point of a solution
containing 6.42 g of sucrose (a nonelectrolyte) in 100.0 g of
water. T f = -0.350 o C T b = 100.096 o C Calculate the freezing
and boiling point of a solution containing 23.7 g of Copper (II)
sulfate (A strong electrolyte) in 250 g of water T f = -2.02 o C T
b = 100.606 o C Calculate the freezing and boiling point of a
solution containing 0.15 moles of the compound naphthalene, a
nonelectrolyte in 175 g of benzene (Normal F.P. = 5.5, Normal B.P.
= 80.1, K f = 5.12, K b = 2.53) T f = 1.1 o C T b = 82.3 o C