Matt Marthaler
Quantitative Analysis: Real World Lab
Determination of Carbonate and Bicarbonate in Soda by Titration
Purpose:
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.
Procedure:
1) 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.
2) Approximately 0.51g of KHP was weighed for three different samples for standardization of the
base.
3) The KHP was dissolved in 25 mL of water, phenolphthalein was added and the solution was
titrated with NaOH.
4) The mL required to reach the endpoint was used to determine the concentration of the base;
the individual calculations were averaged to determine molarity.
5) 25 mL of each cold, fresh soda was measured in a graduated cylinder. Four sodas were used:
Sprite, Sprite Zero, Sierra Mist Natural, and Diet Sierra Mist Natural.
6) The sample was then placed in a beaker with a magnetic stir bar.
7) Methyl orange indicator was added to the solution.
8) The solution was titrated with NaOH over a stir plate until an approximate endpoint was
reached.
9) 25 new mL of each cold, fresh soda was measured in a graduated cylinder. Four sodas were
used: Sprite, Sprite Zero, Sierra Mist Natural, and Diet Sierra Mist Natural. These samples were
separate from the previous samples.
10) The sample was then placed in a beaker with a magnetic stir bar.
11) Phenolphthalein indicator was added to the solution
12) The solution was titrated with NaOH over a stir plate until an approximate endpoint was
reached.
13) The relative percent carbonate and bicarbonate within Sprite, Sprite Zero, Sierra Mist Natural,
and Diet Sierra Mist Natural was then calculated along with the standard deviation from these
titrations.
Data:
Standardization of NaOH
Trial
1
2
3
Average
Standard
Deviation
Mass KHP
(g)
0.5084
0.5090
Volume
NaOH 1 (mL)
26.64
29.90
Molarity
NaOH (M)
0.09345
0.08420
Mass KHP
(g)
0.5092
0.5080
0.5061
Volume
NaOH 2 (mL)
26.59
26.61
26.50
0.0888
Molarity
NaOH (M)
0.09377
0.09348
0.09352
0.09359
0.006547
0.00015716
Titration of Bicarbonate Using Methyl Orange
Trial
1
2
3
Average
Standard
Deviation
(%)
mL
NaOH in
Sprite
0.67
0.70
0.63
[HCO3-]
0.002380
0.002238
0.002238
0.002285
mL
NaOH in
Sprite
Zero
1.00
0.81
1.31
0.000082
[HCO3-]
0.003552
0.002948
0.004653
0.003717
mL
NaOH in
Sierra
Mist
Natural
1.60
1.50
1.42
0.000864
[HCO3-]
0.005990
0.005615
0.005316
0.005640
mL
NaOH in
Diet
Sierra
Mist
1.49
1.58
1.27
0.000378
[HCO3-]
0.005292
0.005612
0.004511
0.005138
0.000566
Titration of Carbonate Using Phenolphthalein
Trial
1
2
3
Average
Standard
Deviation
(%)
mL
NaOH in
Sprite
17.41
17.99
16.11
[CO32-]
0.1237
0.1278
0.1144
0.1197
0.0074
mL
NaOH in
Sprite
Zero
17.91
17.01
18.51
[CO32-]
0.1272
0.1208
0.1314
0.1227
0.0071
mL
NaOH in
Sierra
Mist
Natural
20.69
18.66
18.11
[CO32-]
0.1549
0.1397
0.1356
0.1378
0.0123
mL
NaOH in
Diet
Sierra
Mist
20.20
20.39
19.86
[CO32-]
0.1435
0.1449
0.1411
0.1432
0.0066
Percent Carbonate and Bicarbonate in Soda in a 20 oz Soda Bottle
Percent
Bicarbonate (%)
Percent
Carbonate (%)
Sprite
Sprite Zero
Sierra Mist Natural
Diet Sierra Mist
0.01394
0.02668
0.03136
0.034408
0.73180
0.75880
0.85920
0.860339
Calculations:
Amount of NaOH Pellets
0.1 moles NaOH x 0.5 L x39.997 g NaOH
= 1.999 g NaOH pellets
1 L NaOH x 1 mole NaOH
Mass KHP
25 mL x 1 L x 0.1 mole NaOH x 1 mole KHP x 204.221 g KHP
= 0.5106 g KHP
1000 mL x 1 L x 1 mole NaOH x 1 mole KHP
Molarity NaOH
0.5106 g KHP x 1 mole KHP x 1 mole NaOH x 1 x 1000 mL
= 0.09345 M
204.221 g KHP x 1 mole KHP x 26.64 mL x 1 L
Bicarbonate (Sprite)
0.0888 𝑚𝑜𝑙𝑒𝑠 𝑁𝑎𝑂𝐻 𝑥 0.67 𝑚𝐿 𝑥 1 𝐿 𝑥 1 𝑚𝑜𝑙𝑒 𝐻𝐶𝑂3 − 𝑥 1000 𝑚𝐿
= 0.002380 𝑚𝑜𝑙𝑒𝑠 𝐻𝐶𝑂3 −/𝐿
1000 𝑚𝐿 𝑥 1 𝑚𝑜𝑙𝑒 𝑁𝑎𝑂𝐻 𝑥 25 𝑚𝐿 𝑥 1 𝐿
Carbonate (Sprite)
0.0888 𝑚𝑜𝑙𝑒𝑠 𝑁𝑎𝑂𝐻 𝑥 17.41 𝑚𝐿 𝑋 2 𝑚𝑜𝑙𝑒𝑠 𝐶𝑜3,2 −
0.1237 𝑚𝑜𝑙𝑒𝑠 𝐶𝑂3,2 −/𝐿
1 𝐿 𝑥 1 𝑚𝑜𝑙𝑒 𝑁𝑎𝑂𝐻 𝑥 25 𝑚𝐿
Percent Bicarbonate (Sprite)
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑜𝑙𝑒𝑠 𝑥 61 𝑔 𝑏𝑖𝑐𝑎𝑟𝑏𝑜𝑛𝑎𝑡𝑒 𝑥 591 𝑚𝐿
= 0.0823854 𝑔 𝑏𝑖𝑐𝑎𝑟𝑏𝑜𝑛𝑎𝑡𝑒
1 𝑚𝑜𝑙𝑒 𝑥 25 𝑚𝐿
(0.0823854 g bicarbonate/591 g Sprite) x 100 = 0.01394%
Percent Carbonate (Sprite)
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑜𝑙𝑒𝑠 𝑥 60 𝑔 𝑐𝑎𝑟𝑏𝑜𝑛𝑎𝑡𝑒 𝑥 591 𝑚𝐿
= 4.244562 𝑔 𝑏𝑖𝑐𝑎𝑟𝑏𝑜𝑛𝑎𝑡𝑒
1 𝑚𝑜𝑙𝑒 𝑥 25 𝑚𝐿
(4.244562 g bicarbonate/591 g Sprite) x 100 = 0.7318%
Conclusion:
Our experiment cannot 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. We have found out that Sierra Mist has more Carbonate and Bicarbonate than Sprite
and also that diet sodas have more carbonation than regular sodas.