Experiment 10
Group 6
Ken Caceres
Christian Daroya
Rubycor Duran
Jomari Galecio
Jessa Pilorin
BSBIO1A
Objectives:
1.
2.
3.
To define solubility
To identify the factors affecting it
To use the solubility class diagram
competently
Solubility

It describes the amount of one substance
(solute) that will dissolve in a specified
amount of another substance (solvent)
under stated conditions
 Solute
- A minor component of a
solution.
 Solution - A homogeneous mixture.
 Solvent - The major component of a
solution.
Soluble – that can be dissolved
 Ex. Ethanol and water
 Insoluble – cannot be dissolved
 Slightly soluble - A very small amount will
dissolve and the solution will be
transparent
 ex. Pentane and water

Solubility
Phenomenon: Like dissolves like
 Polar solute dissolves polar solvent
Ex. NaCl is soluble in water
 Nonpolar solute dissolves nonpolar solvent
 Ex. Pentane and benzene
Factors
1. Van der Waals forces
2. Dipole forces between polar molecules
3. Hydrogen bonding
4. Branching in some compounds
5. Functional groups

1.Van der Waals Forces (VWF)

These are forces
between 2
nonpolar
compounds

Non-polar liquids
dissolve to each
other because of
VWF
Ion-induced dipole attraction

a type of VWF which is
a weak attraction that
results when the
approach of an ion
induces a dipole in an
atom or in a nonpolar
molecule by disturbing
the arrangement of
electrons in the
nonpolar species.
2. Dipole – dipole interaction
 Forces
between 2
polar compounds
 Cause
of polar
liquid’s solubility to
each other
 Positive
and
negative ends
attract each other
3. H Bonding

these occur
between polar
covalent molecules
that possess a
hydrogen bonded to
an extremely
electronegative
element, specifically
- N, O, and F

Lower alcohols (low
MW) are soluble in
water because the
attraction between the
OH (hydroxyl group) of
water and alcohol are
similar to those between
individual water /
alcohol molecules
Legend:
= Hydrogen bond
= Oxygen
= Hydrogen
Increase in carbon chain length, in highmolecular weight alcohols, decreased
water solubility
 This is because the strength of VWF
increases with the increasing chain length

Branching in some compounds
favors solubility in water
Because branched carbon chains will not
allow close approach of the branched
molecules
 Thus leading to a decreased VWF and an
increased H bonding

Functional groups
Solubility in water indicates the presence
of OH group
 Solubility in a basic solvent (NaHCO3)
indicates the presence of an acidic
functional group
 Ex. Solubility of benzoic acid in NaHCO3
with –COOH (carboxyl group) as
functional group.

Solubility Class of Organic
Compounds
= determines the
possible functional
group classes to
which the unknown
may belong
S1
These are very polar
compounds which consist
of salts of carboxylic acids
or amines.
 It is also possible the
compound is of low
molecular weight and has
many polar functional
groups such as a
carbohydrate.
 Low mol. Wt. (MW) amines

S2


These compounds are low
molecular weight (generally
less than 5 carbons) with a
polar functional group such
as carboxylic acid, amine,
alcohol, aldehyde, or
ketone.
Low MW carboxylic acids
SOLUBILITY TEST ANALYSIS:
A1


Higher molecular weight
carboxylic acids fall into
this class.
Strong acids
A2


Phenols show this kind of
solubility.
Weak acids
SOLUBILITY TEST ANALYSIS:
B1


Primary, secondary and
tertiary amines fall into this
class.
However, if there are two
or more phenyl groups on
the nitrogen, the amine will
probably not be basic
enough to form the salt and
will, then, be insoluble.
N1

These are higher molecular
weight compounds
(generally more than 9
carbons) containing an
oxygen atom.
SOLUBILITY TEST ANALYSIS:
N2

These are medium size
molecules (generally
containing from 5 to 9
carbons) containing an
oxygen atom.
INERT

These are neutral
compounds. Alkyl halides
and alkanes fall into this
class.
SOLUBILITY TEST ANALYSIS:
Test Compounds
Urea
Molecular Structural
Formula
Formula
O
CO(NH2)2
C
H 2N
NH2
Common
name
Properties
 MW:
60.06g/mol
 Carbamide
 Appears as a
resin
white solid
 Isourea
 MP:133135°C
Urea
Distilled H2O
soluble
Ether
Insoluble
NaOH
Soluble
NaHCO3
Soluble
HCl
Soluble
H2SO4
Soluble
H3PO4
soluble
Solubility Class
S2
Benzoic acid
IUPAC
Name
Common
Name
Molecular
Formula
Benzoic acid
Benzenecarboxylic acid
C7H6O2
Structural
Formula
Benzoic acid and distilled water
Insoluble to cold water but
can be soluble to hot water
 Water-solubility of
carboxylic acids decrease as
the number of carbons
increase. In case of benzoic
acid, the molecule contains
seven carbons and six of
them form a benzene ring.

Benzoic acid and Ether
Soluble
 Benzoic acid is soluble in
ether due to the low
polarity of its molecules
and weak intermolecular
forces.

Benzoic acid and NaOH
Soluble
 NaOH helps
deprotonate benzoic
acid
 organic acids (such as
carboxylic acids) react
with bases to form
water soluble salts
 Either strong/weak
acid

R-COOH + Na+ + OH- + H2O → R-COO- Na+ + OH- +
H3O+
Benzoic Acid and NaHCO3
soluble
 NaHCO3 is a weak base
that reacts with organic
acids to form water
soluble salts
 Solubility to NaHCO3
makes it a strong acid or
Class A1

Benzoic Acid and HCl
Insoluble
 HCl cannot dissolve
benzoic acid because
it is a nonpolar
compound.
 Benzoic acid can’t
loose a proton (H+)
just like HCl

Benzoic Acid and H2SO4
Insoluble
 H2SO4 cannot
dissolve benzoic acid
because it is a
nonpolar compound.
 Benzoic acid can’t
loose a proton (H+)
just like H2SO4.

Benzoic Acid and H3PO4
Insoluble
 H3PO4 cannot
dissolve benzoic acid
because it is a
nonpolar compound.
 Benzoic acid can’t
loose a proton (H+)
just like H3PO4
