Solutions
Mixtures
• A substance made up of 2 or more elements
or compounds that are not chemically
combined and can be separated
• 2 classifications
1. Homogeneous--> mixtures that are
spread out evenly
Ex. solutions
2. Heterogeneous--> mixtures are not
spread out evenly
Ex. Colloids and suspensions
KoolAid & Salt Water are
examples of Homogeneous
Mixtures
Rice Krispy Bars, Paint & Pizza are examples of
Heterogeneous Mixtures
What is a solution?
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A homogeneous mixture
Ex. saltwater
Made of 2 parts
1. Solute--> the substance that is
considered to be dissolved (salt)
• 2. Solvent--> the substance in which
the solute is dissolved (H2O)
How can you tell which is the
solute and solvent?
• If 2 substances in the solution were in
different phases, the one that changed phase
is the solute (salt), and the substance that did
not change phase is the solvent (H2O)
• If 2 substances are in the same phase
originally, the substance in smaller amount is
usually the solute (40 g alcohol), and the
substance is greater quantity is usually the
solvent (60 g H2O)
Which is the solute and
solvent?
• 75% Cu and 25% Zn = brass alloy
• CO2(g) and H2O(l) =
carbonated beverage
• O2(g) and air
Properties of Solutions
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Very small particle size: .01 nm-1 nm
Do not separate upon standing
Are transparent
Cannot be separated by filtration
Particles do not display the Tyndall
Effect: the particles are too small to
scatter light
Examples of Solutions
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Sucrose in H2O
Food coloring in H2O
Sodium Borate in H2O
Carbonated Beverages
Alloys (2 or more metals)
H2O vapor in air
Colloids
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A heterogeneous mixture
May or may not be transparent
Medium particle size: 1 nm -1000 nm
Do not separate upon standing
Cannot be separated by filtration
Particles display the Tyndall Effect: the
particles are large enough to scatter light
Examples of Colloids
• Gelatin in H2O
• Milk
• Clouds
Suspensions
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A heterogeneous mixture
Are not transparent
Large particle size: over 1000 nm
Particles settle out
Can be separated by filtration
May or may not display the Tyndall
Effect
Examples of Suspensions
• Clay in H2O
• Cooking oil in H2O
• Spoiled milk
More about Solutions
• Solutions in which H2O is the solvent are
called aqueous
• If H2O cannot act as the solvent, another
liquid will
Ex. CCl4 & C6H6 will act as fat solvents in the
body
• Solutions in which alcohol is the solvent are
called tinctures
Ex: Betadine solution (I2 crystals dissolved in
CH3OH)
• When 2 liquids dissolve in one another, they
are said to be miscible
• When 2 liquids do not dissolve in one
another, they are said to be immiscible
• Make sure to use these terms when
describing the solubility of liquids in one
another!!!
• Ex. Ethanol is miscible in H2O
• Ex. Oil is immiscible in H2O
• Alloys are solutions made up of 2 or
more metals
• Ex. Brass 70%Cu and 30% Zn
• Ex. Sterling silver (Cu & Silver)
• Ex. Amalgam--> an alloy made Hg and
other metals that is used to make dental
fillings
Why can we make so many
aqueous solutions?
• H2O is known as the “universal solvent” because it can dissolve
or be miscible with most polar substances
• ***Remember the “Like” dissolves “like” rule
+
• Polar substances have an unequal distribution of electron
charge because of certain elements stronger or weaker desires to become a noble gas within the compound
• Ex. NaCl, C12H22O11, ethanol (C2H5OH)
+
• Nonpolar substances have equal distribution of electron charge
because all elements within the compound have the same
desire to become a noble gas
• Ex. Kerosene (CxHy), oil, ethane (C2H6)
What makes something an
electrolyte?
• An electrolyte is a substance that dissolves in
H2O that conducts an electric current
• A substance must have ions (+ and - charged
particles) to be an electrolyte
• Electrolytes may be classified as “strong” or
“weak” depending on how many ions they
produce in solution
• Examples include: sodium chloride (NaCl),
potassium phosphate (K3PO4)
• A nonelectrolyte is a substance that
dissolves in H2O that does not conduct
an electric current
• Nonelectrolytes are polar or nonpolar
covalent compounds.
• Examples include: sucrose C12H22O11
(polar), pure water H2O (polar), and
iodine I2 (nonpolar)
How can we increase the rate
of dissolution?
• Rate of Dissolution--> the measure of how
fast a substance dissolves
• Increase surface area of solute
• Increase the temperature
• Agitate the solution (stir)
• Increase the concentration of solvent so more
particles come in contact with the solute
What is solubility?
• Solubility is the maximum amount of solute
that can dissolve in a certain amount of
solvent
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What main factors affect solubility?
1. Temperature
2. Pressure
3. Nature of the solute (polar vs. nonpolar)
Temperature as a factor
• As you increase the temperature of a solid or liquid,
solubility increases
By increasing the kinetic energy, the solvent particles are
forced to come in contact with the solute particles more
often and can take on more as a result
• As you increase the temperature of a gas, solubility
decreases
By increasing the kinetic energy, the gas particles are
moving too quickly and leave the solution before they
have a chance to collide with the solute (gases do not
want to be put in a liquid solution!!!)
Pressure as a factor
• An increase or decrease in pressure of a solid or liquid in
solution will have no affect on the solubility of that solution
This is because there is little to no ability (or space
between particles) to compress or expand solid or liquid
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An increase in pressure will increase the solubility of a
gas
This is because gas particles can be forced closer
together (or farther apart) due to the large spacing
between particles
What is saturation?
• When a solution has the maximum
amount of solute dissolved in a certain
amount of solvent at a given
temperature, it is said to be saturated
• Saturated solutions are said to be in
equilibrium
• rate of solute dissolving in solvent
rate of solute crystallizing in solvent
Solubility Curve
All data points on the
line represent a
saturated solution
Unsaturated versus Saturated
Solutions?
• When a solution contains less solute than it
could at a certain temperature, it is said to be
unsaturated
• When a solution contains more solute than it
normally could at a certain temperature, it is
said to be supersaturated
***This is a dynamic condition that is very
unstable
Solubility Curve
All data points above the
saturation line represent a
supersaturated solution
All data points below the
saturation line represent
an unsaturated solution
Solubility Curve for Gases
• Gases have too much kinetic energy
and do not want to be dissolved in a
liquid
• When temperature increases, solubility
decreases for gases
More on gases…
• Henry’s Law--> the solubility of gases
in a liquid is directly proportional to the
partial pressure of that gas on the
surface of that liquid
• Effervescence--> the rapid escape of
gas from a liquid in which it dissolves
Dilute Versus Concentrated
Solutions
• Dilute--> a low amount of solute is dissolved
in a solvent
• Concentrated--> a high amount of solute is
dissolved in a solvent
• These terms will not tell us whether a solution
is saturated, unsaturated, or supersaturated
• The concentration of a solution can be found
using the Molarity (M) and Molality (m)
equations
Molarity
• M = moles of solute / L of solution
• Solution = solute + solvent
• Sample problem : How many grams of
sodium chloride can be dissolved in 150. mL
of water to make a .85 M solution?
• What is the molarity of a solution made
up of 150. mL of ethanol (C2H5OH) in
200. mL of water? Dethanol = .789 g/mL,
Dwater = 1.00 g/mL
Molality
• m = moles of solute / kg of solvent
• Sample problem : How many grams of
CCl4 are needed to dissolve 28 g of I2 to
make a .050 m solution?
• A solution containing 468 g of sucrose
(C12H22O11) per liter has a density of
1.18 g/mL. What is the molality of this
solution?
How to make a dilute solution
from a concentrated solution?
M1V1 = M2V2
concentrated
dilute
M = molarity
V = volume
Sample problem: How much 12 M HCl do you need to
make 500. mL of a 3.0 M HCl solution? How much
water did you add to the concentrated 12 M solution?
• How much water would you need to
make .850 L of 6.8 M sulfuric acid
solution for 18 M solution?