Lesson 5-9 - Types of Solutions

Solutions

Mixtures of two or more substances evenly distributed throughout a single phase

Solutions

Atoms, ions, or molecules are thoroughly mixed in this such that each part of the mixture has uniform composition and properties

Solutions

Consists of a solute and solvent

Solute

substance dissolved in a solution and is usually present in smaller amount

Solvent

dissolving medium

Unsaturated
Saturated
Supersaturated

Classifications of Solution

Unsaturated

contains less solute than solvent’s capacity to dissolve

Unsaturated

this means that the solution can still dissolve more solute

Unsaturated

a solution contains less than the amount of the solute that can be held at equilibrium

Saturated

contains the maximum amount of solute that the solvent can dissolve at a certain temperature

Supersaturated solution

contains more dissolved solute than is present in a saturated solution

seed crystal

Supersaturated solution

this type is unstable such that the excess solute can crystallize in the solution by adding a “seed crystal” (a process called seeding) or by scratching the sides of the container

Supersaturated solution

a solution containing more solute than it would contain equilibrium

Overcoming the intermolecular forces in the solvent to give room for the solute - “expanding the solvent”

Separating the solute into its individual components - “expanding the solute”

Allowing the solute and the solvent to interact to form the solution

FORMATION OF A LIQUID SOLUTION

Endothermic

Steps 1 and 2 require energy to overcome the forces in expanding the solvent and solute

Exothermic process

Step 3 involves the formation of new solute-solvent interactions, which usually releases energy

Enthalpy Change (ΔH)

Each of the three steps involves a heat change

(ΔHsoln)

Enthalpy change associated with the formation of the solution

(ΔHsoln)

Equal to the sum of ΔH values for the three steps

ΔH₁ + ΔH₂ + ΔH₃ 

ΔHsoln

endothermic process

Positive ΔHsoln

exothermic process

Negative ΔHsoln

Exothermic

more energy is released when new bonds form than is used when bonds are broken

Endothermic

more energy is used when bonds are broken than is released when new bonds are formed

Concentration of Solution

Measure of the amount of solute in a given amount of solvent or solution

Concentration of Solution

One type of solution may be prepared and expressed in different concentrations

Mass

percent of weight (%w/w)

Volume

percent by volume (%v/v)

Volume

involves the volume of both the solute and the solution

%w/w and %v/v

unit of their components should be expressed in the same unit

Mass-volume

percent by weight-volume (%w/v)

Mass-volume

when using density in calculation, use density as a conversion factor to obtain either mass or volume of the solution

Mole fraction

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

Mole fraction

sum of this of all components in a solution will always be equal to one

Molality

number of moles of solute per kilogram of solvent

molal (m)

Molality unit

Morality

number of moles of solute per liter of solution

Molarity

useful in doing stoichiometric calculations involving solutions

molar (M)

Morality unit

Part per million (ppm)

expresses the number of parts of solute per one million parts of the solution

Part per million (ppm)

usually to describe the concentration of relatively small levels of solute in solution such as contaminant or pollutants

Part per million (ppm)

expressed in other units depending on the given information

Mass, Volume, Mass-Volume, Mole Fraction, Molality, Morality, Part per Million

Concentration of Solution