Solutions
Chapter 5
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Why is this topic important in the class?
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Solutions
„
A solution is a homogeneous
mixture of two or more pure
substances.
„
The solvent is the one in the
largest quantity.
„
The solute is the one in the
smallest quantity.
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Concentration of Solutions
„
Quantity of solute dissolved or mixed with a
solvent.
„
Saturated – contains the maximum amount of
solute that can be dissolved at a temperature
reported as grams per 100 g solvent
„
Unsaturated - contains less than the maximum
amount of solute. Will result in a homogeneous
mixture.
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Solubility
„
Is determined by the intermolecular forces that
occur between particles of solute and solvent.
„
Polar solutes dissolve in polar solvents.
„
Nonpolar solutes dissolve in nonpolar solvents.
“Like dissolves like.”
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Type of Solutes
„
Covalent compounds – molecules are units that do
not break apart when mixed with a solvent.
„
Examples –
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Type of Solutes
„
Ionic compounds – when in solution the ions do not stay
together; they separate. Known as electrolytes
Examples –
„
How many ions are present in in sodium phosphate?
„
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Concentration
„
„
amount of solute
amount of solution
„
Amount of solution = amount solute + amount solvent
„
Could be in different units:
Grams
Volume
moles
„
„
„
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Percent by Mass and Volume
part
Percent =
x 100
whole
Percent concentration can be expressed as:
grams solute
x 100
% (mass/mass) =
grams solution
grams solute
% (mass/volume) =
x 100
mL solution
volume solute
x 100
% (volume/volume) =
volume solution
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Lets Practice!
„
What is the % by mass when 20 grams of glucose is
dissolved in 75 grams of water?
„
A) 21 %
b. 27 %
c. 3.8 %
d. 0.27 %
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Molarity
Molarity (M) is moles of solute per liter of solution.
moles of solute
M =
Liters of solution
What is the molarity when 125.0 grams of glucose, C6H12O6 , are
dissolved in water to make a 3.0 L of solution? MM 180 g/mol
a. 2.1 M
b. .694 M
c. 0.23 M
d. 0.48 M
e. 1. 4M
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Molarity
A 1.5 L blood sample is analyzed for the presence of carbon
dioxide and found to contain 235 mg. What is the molarity of the
solution?
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Diffusion and
Osmosis
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Substances move from
areas of higher
concentration to those of
lower concentration in a
process called diffusion.
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•The net movement of water across a membrane
from a solution of lower concentration to one of
higher concentration of ions is called osmosis.
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•The pressure exerted by water as it flows through
a semipermeable membrane is called osmotic
pressure.
•The greater the difference in solute concentrations
across the semipermeable membrane, the greater
the osmotic pressure.
•Cell membranes are semipermeable and are,
therefore, affected by osmosis.
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