Acid-Base Titration (HL Chemistry Lab II)
I. INTRODUCTION
An “Acid-Base Titration” is the determination of the concentration of a
given volume of acid or base by fully neutralizing it by a given volume
of acid or base with a known concentration. By finding out the amount
of acid or base needed, we can work out the concentration of the
unknown substance using our quantitative data and knowledge of the
concentration formula (C=n/V).
Hydrochloric acid (HCl) is a clear and odorless solution of hydrogen and
chloride in water. Its relative molecular mass is 36.5 g/mol. It is also a
very strong acid due to its high concentration of hydrogen cations - the
reason for its fairly low pH.
Sodium Hydroxide (NaOH) is a strong alkali that is used to neutralize
acidic substances and produce metal salts. Its relative molecular mass is
31 g/mol. At room temperature the alkali is a crystalline odorless solid,
however it is usually dissolved in water due to its strong alkali properties
that come from the high concentration of hydroxide anions.
Phenolphthalein is a liquid indicator with the color purple. In pH of less
than 8.5 (acidic conditions) it is clear whereas in neutral conditions it is
pink. The change in color of the indicator is due to the change in its
molecular structure. Therefore it is a common indicator used in titration
experiments.
In this experiment we will be investigating the unknown concentration
of a given volume of hydrochloric acid by finding out the amount of
base (sodium hydroxide) needed to neutralize it through the process of
“Acid-Base Titration”. The indicator we will use is phenolphthalein. We
will carry out three trials to get an average, and in every trial we will aim
to get the faintest pink color possible (this shows the minimum amount
of alkali needed to neutralize the acid).
, II. METHODOLOGY
Variables
Our dependent variables are the concentration of hydrochloric acid and
color of solution of products (we will try to get the faintest pink color
possible, however, the darkness of the color will vary per trial).
Our independent variable is the amount of NaOH required to neutralize
the acid.
Our control variables are the volume of hydrochloric acid used, the room
temperature (16 degrees Celsius), the type of indicator (phenolphthalein)
the amount of phenolphthalein indicator, and the concentration of
NaOH.
Materials
1. Pipette
2. Phenolphthalein indicator
3. Erlenmeyer flask
4. Burette
5. 75 mL of HCL with unknown concentration (analyte)
6. NaOH with 0.5 M (titrant)
7. Stand and clamp
8. Lab coats
9. Beaker
10. White piece of paper
Safety Hazards
In every scientific experiment it is crucial to take several safety
precautions to ensure that no one or nothing is harmed during the
procedure. In our titration we made sure to put on lab coats and wash our
hands immediately after the experiment so that there is no chemical
I. INTRODUCTION
An “Acid-Base Titration” is the determination of the concentration of a
given volume of acid or base by fully neutralizing it by a given volume
of acid or base with a known concentration. By finding out the amount
of acid or base needed, we can work out the concentration of the
unknown substance using our quantitative data and knowledge of the
concentration formula (C=n/V).
Hydrochloric acid (HCl) is a clear and odorless solution of hydrogen and
chloride in water. Its relative molecular mass is 36.5 g/mol. It is also a
very strong acid due to its high concentration of hydrogen cations - the
reason for its fairly low pH.
Sodium Hydroxide (NaOH) is a strong alkali that is used to neutralize
acidic substances and produce metal salts. Its relative molecular mass is
31 g/mol. At room temperature the alkali is a crystalline odorless solid,
however it is usually dissolved in water due to its strong alkali properties
that come from the high concentration of hydroxide anions.
Phenolphthalein is a liquid indicator with the color purple. In pH of less
than 8.5 (acidic conditions) it is clear whereas in neutral conditions it is
pink. The change in color of the indicator is due to the change in its
molecular structure. Therefore it is a common indicator used in titration
experiments.
In this experiment we will be investigating the unknown concentration
of a given volume of hydrochloric acid by finding out the amount of
base (sodium hydroxide) needed to neutralize it through the process of
“Acid-Base Titration”. The indicator we will use is phenolphthalein. We
will carry out three trials to get an average, and in every trial we will aim
to get the faintest pink color possible (this shows the minimum amount
of alkali needed to neutralize the acid).
, II. METHODOLOGY
Variables
Our dependent variables are the concentration of hydrochloric acid and
color of solution of products (we will try to get the faintest pink color
possible, however, the darkness of the color will vary per trial).
Our independent variable is the amount of NaOH required to neutralize
the acid.
Our control variables are the volume of hydrochloric acid used, the room
temperature (16 degrees Celsius), the type of indicator (phenolphthalein)
the amount of phenolphthalein indicator, and the concentration of
NaOH.
Materials
1. Pipette
2. Phenolphthalein indicator
3. Erlenmeyer flask
4. Burette
5. 75 mL of HCL with unknown concentration (analyte)
6. NaOH with 0.5 M (titrant)
7. Stand and clamp
8. Lab coats
9. Beaker
10. White piece of paper
Safety Hazards
In every scientific experiment it is crucial to take several safety
precautions to ensure that no one or nothing is harmed during the
procedure. In our titration we made sure to put on lab coats and wash our
hands immediately after the experiment so that there is no chemical
