Rachel Jarrett
Matt Marthaler

In this experiment, we will determine the
concentration of carbonate and bicarbonate
species in different sodas using the technique
of titration. A primary standard used in this
experiment is NaOH for the direct titration of
the diprotic acid. Color indicators which
utilize changes in pH will be used to
determine the presence of the different
species of the acid.




Approximately 2 g of NaOH(s) pellets were placed
in a 500mL volumetric flask and diluted to the
mark with distilled water to make an
approximate 0.1M solution.
Approximately 0.51g of KHP was weighed for
three different samples for standardization of the
base.
The KHP was dissolved in 25 mL of water,
phenolphthalein was added and the solution was
titrated with NaOH.
The mL required to reach the endpoint were used
to determine the concentration of the base; the
individual calculations were averaged to
determine molarity.




25 mL of each cold, fresh soda was measured
in a graduated cylinder.
The sample was then placed in a beaker
Methyl orange indicator was added to the
solution
The solution was titrated with NaOH until an
approximate endpoint was reached



Color of this indicator changes from yellow
to orange to red at pH between 3.1 and 4.4
At a strong orange, all carbonic acid has
turned into bicarbonate and indicates a pH
around 3.7
This color difference was difficult to
determine




25 mL of each cold, fresh soda was measured
in a graduated cylinder. These samples were
separate from the previous samples.
The sample was then placed in a beaker
Phenolphthalein indicator was added to the
solution
The solution was titrated with NaOH until an
endpoint was reached


Color of this indicator changes from
colorless in an acidic solution to
pink/purple in a basic solution
At pink/purple, all bicarbonate has turned
into carbonate

Amount of NaOH Pellets
0.1 moles NaOH x 0.5 L x 39.997 g NaOH
1 L NaOH
1 mole NaOH
= 1.999 g

Mass KHP
25mL x
1L
x 0.1mole NaOH x 1 mole KHP x 204.221g KHP
1000mL
1L
1 mole NaOH
1 mole KHP
=0.5106 g

Molarity NaOH
0.5106g KHP x 1 mole KHP x 1mole NaOH x
1 x 1000mL
204.221g
1mole KHP
26.64mL
1L
=0.09345 M

Bicarbonate (Sprite):
0.0888 moles NaOH x 0.67 mL x 1 L x 1 mole HCO3- x
x 1,000 mL
L
1,000 mL 1mole NaOH
25 mL
L
= 0.002380 moles HCO3- / L

Carbonate (Sprite):
0.0888 moles NaOH x 17.41 mL x 2 moles CO32- x
L
= 0.1237 moles CO32- / L
1 mole NaOH
25 mL
_

Bicarbonate (Sprite):
average moles x 61 g bicarbonate x 591 mL
mole
25 mL
= 0.0823854 g bicarbonate x 100
591 g Sprite
= 0.01394%

Carbonate (Sprite):
average moles x 60 g carbonate x 591 mL
mole
25 mL
= 4.244562 g carbonate x 100
591 g Sprite
= 0.7318%
Our experiment can not be considered entirely accurate, but it was not a failure.
Some of the inaccuracies come from:
 Re-standardization of more NaOH due to a short supply of the solution in the
middle of the experiment

Inconsistencies due to the gradual color change of methyl orange. We did not
know when to stop the titration since the color of orange is difficult to read
consistently.
 Due to the carbonation in soda, a graduated cylinder was used to measure the
volume of soda since the bubbles made it impossible to use a pipet.
 The density of water was used to calculate the percent carbonate and bicarbonate
since there are not published values for the density of the different sodas
 When measuring the acidity of these beverages, other acids present in the soda
such as citric acid can distort the perception of carbonic acid and change results.
Regardless of the possible reasons for error, the standard deviations of this
experiment were reasonable, so precision was achieved within the calculations.
The amount of carbonate and bicarbonate were determined, therefore, the
experiment was successful and error can be acknowledged.