Solutions
Homogeneous Mixtures - Solute & Solvent
Objectives
Identify various types of solutions
Define solubility and the factors that affect it
Correctly use the terms unsaturated, saturated and
supersaturated
Understand how to read a solubility graph
Express concentration in terms of molarity
Calculate the molarity of diluted solutions
Types of Solutions
Type
Example
Solvent
Solute
Air
N2
O2
Gas in Liquid
Carbonated H2O
H 2O
CO2
Liquid in Liquid
Vinegar
H 2O
Acetic Acid
Solid in Liquid
Ocean Water
H 2O
NaCl
Liquid in Solid
Dental Amalgam
Ag
Hg
Solid in Solid
Steel
Fe
C
Gas
Gas in Gas
Liquid
Solid
Solvent and Solute
Solvent is the substance in the mixture in the greatest
amount
Solute is the substance in the mixture in the lesser
amount
Solvation
Process of surrounding solute particles with solvent particles
Solvation of ionic compound produces electrolyte (ions in solution
- can conduct electricity)
Solvation of molecular compounds does not produce electrolyte
Which of the following would be a nonelectrolyte?
HCl (hydrochloric acid)
NaOH (sodium
hydroxide)
CaCl2 (calcium chloride)
C12H22O11 (sucrose)
Solubility
Situation: you add more
and more sugar to your
iced tea - sugar crystals
start to collect at bottom
of glass
Only a limited amount
of solute can dissolve in
a certain amount of
solvent at a given set of
conditions
Solubility
Solubility = maximum
amount of solvent that
will dissolve in a given
amount of solvent at a
specific temperature
and pressure
Factors that affect Solubility
Temperature
Pressure
Agitation
Breakage into small
particles
Solubility Graph - Solids
Most solids are more
soluble as temperature
of solution increases
Greater kinetic energy
of solvent helps
surround solute
particles
Solubility Graph - Gases
Most gases are less
soluble as temperature
of solution increases
Greater kinetic energy
helps gases escape
intermolecular forces
attracting them to
solvent particles
Question
Given the following
solubility curve for a
particular solute in
water, do you think the
solute is a gas or a
solid?
Saturated Solution
Saturated solution
contains the maximum
amount of dissolved
solute for given solvent
amount at particular
temperature and
pressure
Same rate of
precipitation (solid
coming out of solution)
as dissolution (solid
Unsaturated Solution
Less than the maximum
amount of solvent in a
solution at particular
temperature and
pressure
More solute can
dissolve and stay in
solution
Supersaturated Solution
More than the maximum
amount of solvent in a
solution at particular
temperature and pressure
Can be made by dissolving
solute in hot solvent and
slowly cooling
Slight disturbance will cause
crystallization
Watch video
Question
You have a glass of
water with salt
dissolved in it.
You add more salt, and
it easily dissolves in the
water.
Is the solution
unsaturated, saturated
or supersaturated?
Concentration
How much solute is
dissolved in a solution
Qualitative expression:
dilute, concentrated
Need quantitative way
to express
concentration
Expressing Concentration
Various quantitative
concentration ratios:
percent by mass, percent
by volume, mole fraction,
molality, molarity
We will focus on molarity this is the most commonly
used to express
concentration of solute in
liquid solution
Molarity
Ratio of moles of solute
to liters of solution
Indicated by M
.85 mol solute in 1 liter
of solution = 0.85 M
0.85 M read as “0.85
molar”
M = moles/liter
Question
What is molarity of
aqueous solution
containing 40.0 g of
glucose (C6H12O6) in 1.5
liter of solution?
First - convert grams of
glucose into moles
molar mass of glucose =
180 g/mol
Molarity Problem Continued
1mol/180 g (40 g) = 0.2
moles
0.2 mole/ 1.5 L = 0.133
M
Problems
What is molarity of bleach solution containing 9.5 g of
NaOCl per liter of bleach?
Calculate the molarity of 1.60 L of a solution
containing 1.55 g of dissolved KBr.
Preparing Molar Solutions
You want to make a 1 L of a 1.5 molar solution of
sucrose (C12H22O11 - molar mass = 342 g/mol). How
much sugar do you need?
First - figure out how many grams of sucrose you
need -
1.5 moles (342 g/mol) = 513 g
Add 513 g of sucrose to volumetric flask. Add water
until 1 liter mark reached.
Amount of water will be less than 1 L. Why?
Diluting Solutions
In labs, we use
concentrated solutions
of standard molarities
called stock solutions
For example,
concentrated HCl is 12
M
You want to have 1 liter
of a 1.5 M solution of
HCl - What do you do?
Preparing Dilutions
M1V1 = M2V2
You want 1 L of 1.5 M HCl
Figure out how much water you need to add:
Solve for V1 - this is how much concentrated solution you
need
V1 = M2V2/M1
V1 = ((1.5 mol/L)(1 L))/(12 mol/L)
V1 = 0.125 L concentrated HCl - mix with DI water to
dilute to 1 L
Questions - Write these down and work
on them
What volume, in mL of 2.00 M CaCl2 stock solution
would you use to make 0.50 L of 0.300M CaCl2
solution?
What volume of a 3.00 M KI stock solution would you
use to make 0.300 L of a 1.25 M KI solution?
How many mL of a 5.0 stock solution would you need
to prepare 100 mL of 0.25 M H2SO4?
If you dilute 20.0 mL of a 3.5M solution to make 100
mL of solution, what is the molarity of the dilute
solution?