Solution
Concentrations
Types of Solutions
• Solutions-mixtures of two or more substances evenly distributed
throughout a single phase.
 Solute- substance dissolved in a solution
 Solvent-dissolving medium
ex: sugar-water solution
Types of Solutions
Solute
Solvent
Solution
Example
Gas
Gas
Gas
Oxygen in nitrogen
Gas
Liquid
Liquid
Carbon dioxide in
water
Gas
Solid
Solid
Hydrogen in
Palladium
Liquid
Liquid
Liquid
Ethanol in water
Liquid
Solid
Solid
Mercury in silver
Solid
Liquid
Liquid
Salt in water
Solid
Solid
Solid
Copper in tin
(Bronze)
Classification of Solution
• Unsaturated solution-contains
less solute than the solvent
• Saturated Solution-contains the
maximum amount of solute that
the solvent can dissolve
• Supersaturated solutioncontains more dissolved solute
than is present in saturated
solution.
Energy of Solution
The formation of a liquid solution takes
place in three steps:
(1)Overcoming the intermolecular
forces in the solvent to give room for
the solute;
(2) Separating the solute into its
individual components; and
(3) Allowing the solute and the solvent
to interact to form the solution.
Concentration of Solutions
•
•
•
•
•
•
Percent by Mass (% w/w)
Percent by Volume ( %v/v)
Percent by Mass-Volume (% w/v)
Mole Fraction
Molarity
Molality
Percent by Mass (% w/w)
• Percent by mass (percent by weight, % w/w) of a solute is given by:
Percent by mass =
=
mass of solute
X 100
mass of solution
mass of solute
mass of solute + mass of solvent
X 100
Percent by Volume (% v/v)
• Percent by volume (% v/v) of a solution involves the volume of both
the solute and the solution.
volume of solute
Percent by volume =
volume of solution
X 100
Percent by Mass-Volume (% w/v)
• Percent by mass-volume (percent weight-volume, % w/v) of a
solution is given by:
mass of solute (grams)
Percent by mass- volume =
volume of solution (mL)
X 100
ppm and ppb
Sample Problem
Express the concentration of a solution in
a) %w/w
b) %v/v
c) %w/v
containing 5 g of NaCl and 50 mL of water. (ρ of water=1 g/mL
and ρ of NaCl=2.16 g/mL)
Sample Problem
1. If 2.85 g of calcium hydroxide is dissolved in enough water to
make 185 g of solution, what is the percent by mass of calcium
hydroxide in the solution?
2. A wine contains 12% alcohol by volume. Calculate the volume (in
mL) of alcohol in 350 mL of the wine.
3. A 50-mL of 12% by mass-volume solution was used in an
experiment. How many grams of the solute does the solution
contain?
Practice Problems
1. Calculate the mass (in grams) of magnesium chloride that would
be needed to prepare 150 mL of a 20% by mass aqueous solution
of the salt. The density of the solution is 1.1 g/mL.
2. Calculate the percent by mass of the solution containing 8.60 g of
salt in 95.0 g of solution.
3. A solution is prepared by dissolving 20-mL of pure hydrogen
peroxide in enough water to make 200-mL of solution. What is the
concentration of the hydrogen peroxide solution?
Molarity and Molality
• Molality, m- number of moles of solute per kilogram of solvent
• Molarity, M-number of moles of solute per liter of solution.
=
Sample Problems (Molality, m)
1. What is the molality of a solution prepared by dissolving 32.0 g of
CaCl2 in 271 g of water?
2. How many grams of glucose (C6H12O6) must be dissolved in 563 g
of ethanol (C2H5OH) to prepare a 2.40 m solution?
3. What is the molality of a solution made by dissolving 15.20 g of I2 in
1.33 mol of diethyl ether, (CH3CH2)2O?
Sample Problems (Molarity, M)
Determine the molarity for each of the following solutions:
1.0.444 mol of CoCl2 in 0.654 L of solution
2. 98.0 g of phosphoric acid, H3PO4, in 1.00 L of solution
3. 0.2074 g of calcium hydroxide, Ca(OH)2, in 40.00 mL of
solution
Sample Problems
1. A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water. What is
the percent by mass of KCl in the solution?
2. Many people use a solution of sodium phosphate to clean walls before putting up
wallpaper. The recommended concentration is 1.7% (m/v). What mass of sodium
phosphate is needed to make 2.0-L of solution?
3. Rubbing alcohol is sold as 70% (v/v) solution of isopropyl alcohol in water. What volume
of isopropyl alcohol is used to make 500-mL of rubbing alcohol?
4. Calculate the amount of water (in grams) that must be added to
(a) 5.00 g of urea in the preparation of a 16.2 percent by mass solution, and
(b) 26.2 g of MgCl2 in the preparation of a 1.5 percent by mass solution.
Mole Fraction (x)
• Mole fraction (x) of a component in a solution is equal to the
number of moles of that component divided by the total number of
moles of all the components present.
• The sum of the mole fractions of all components in a solution will
always be equal to one (1).
Sample Problem
1. Calculate the mole fraction of sulphuric acid (H2SO4) in 8% (w/w)
aqueous H2SO4 solution. (MM of H2SO4 =98 g/mol; MM of
H2O=18 g/mol)
2. Calculate the mole fraction of each component of a solution
containing 65 g ethanol (C2H6O) in 350 g of water.
3. What are the mole fraction of hydrochloric acid (HCl) and water in
20% (w/w) aqueous solution.