Acid/Base Neutralization
• The addition of a strong acid to a strong base can result in
its neutralization
• Remember, in a neutral solution the hydroxide and
hydronium ion concentration are equal
• Which leads to a pH of 7.0
• Usually the chemical reaction for a neutralization reaction is
as follows:
Acid + Base  Salt + Water
Titrations
• Titrations refer to the procedure
in which a solution of known
concentration (a standard) is
used to identify a solution of
unknown concentration
• This usually involves a piece of
chemistry equipment known as
a buret.
Titrations
• Conducting a titration continues
until you reach the equivalence
point.
• Think of the equivalence point
as the point in which the
standard and the unknown
solutions exactly react with one
another
Titrations
• As acids and bases are commonly colorless, in order to
ascertain whether or not a titration is complete we may add
an indicator to the unknown solution.
• Indicators change color at specific pH values.
Titrations
• If we use an indicator in a titration, the instant at which the
indicator changes color represents the end point of the
titration.
• Ideally you would want to choose an indicator with the same
endpoint as the expected equivalence point of the titration.
The endpoint occurs the
instant the color changes
Strong Acid/Base Titration
Calculations
•
•
We will primarily deal with strong acid and base titrations.
At the equivalence point, the number of moles of hydroxide will be equal to
hydronium.
MolesAcid = MolesBase
•
This can then be rearranged using what we know about solutions to…
# of EquivalentsAcid x VolumeAcid x ConcentrationAcid = # of EquivalentsBase VolumeBase x ConcentrationBase
•
For example, suppose you have 40.00mL of an HCl solution of an unknown
concentration. It takes 24.64mL of a 0.5500M NaOH solution to reach the
equivalence point. What is the concentration of HCl?
# of Ions
• This is dependent on the chemical formula of the acid and
base.
• For example, the following strong acids and bases have a
single ion:
– HCl and NaOH
• For example, the following strong acids and bases have two
ions:
– H2SO4, Ca(OH)2
Titration Calculation Sample
• For example, suppose you have 40.00mL of an HCl solution of
an unknown concentration. It takes 24.64mL of a 0.5500M
NaOH solution to reach the equivalence point. What is the
concentration of HCl?
IonsAcid = 1.0
VAcid = 0.040L
CAcid = unknown
IonsBase = 1.0
VBase = 0.02464L
CBase = 0.5500M
IonsAcid x VAcid x CAcid = IonsBase x VBase x CBase
1.0 x 0.040L x CAcid = 1.0 x 0.02464L x 0.5500M
CAcid = 0.339M
Titration Calculation Sample
• If 20.6mL of 0.010M aqueous HCl is required to titrate 30.0mL
of an aqueous solution of NaOH to the equivalence point, what
is the molarity of the NaOH solution?
IonsAcid = 1.0
VAcid = 0.0206L
CAcid = 0.010M
IonsBase = 1.0
VBase = 0.030L
CBase = unknown
IonsAcid x VAcid x CAcid = IonsBase x VBase x CBase
1.0 x 0.0206L x 0.010M = 1.0 x 0.030L x CBase
CBase = 0.00687M
Titration Calculation Sample
• If 20.6mL of 0.010M aqueous HCl is required to titrate 30.0mL
of an aqueous solution of Ca(OH)2 to the equivalence point,
what is the molarity of the Ca(OH)2 solution?
IonsAcid = 1.0
VAcid = 0.0206L
CAcid = 0.010M
IonsBase = 2.0
VBase = 0.030L
CBase = unknown
IonsAcid x VAcid x CAcid = IonsBase x VBase x CBase
1.0 x 0.0206L x 0.010M = 2.0 x 0.030L x CBase
CBase = 0.00343M