determination of the concentration of citric acid using acid base titration
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Determination of the Concentration of Citric Acid Using Acid Base TitrationTRANSCRIPT
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THEME: ANALYSIS ON
CONTAMINANTS AND ADDITIVES
IN CONSUMER PRODUCTS
Determination of the concentration of
citric acid in soft drinks using acid/base
titration
NAME:
I/C NUMBER:
INDEX NUMBER:
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ABSTRACT
Citric acid is often added to food and beverages to improve the
flavor. The purpose of this project is to determine the concentration of
citric acid in soft drinks by using acid/base titration.
In this project, the technique of titration is adopted by reacting the
soft drinks that contain citric acid with sodium hydroxide solution. Six
types of soft drinks are used in this project, which are 7-UP,Revive,Ice-
Cream Soda,Mountain Dew,Pop and100 Plus. 25.00cm3 of soft drink
with unknown molarity of citric acid is titrated with a standard 0.1mol dm-3
NaOH solution. Phenolphthalein is used as an indicator to determine the
endpoint of the titration.
The results obtained are used to calculate the molarity of citric acid
in the soft drinks and thus the number of moles, the average number of
moles, and the average grams of moles of citric acid per can or bottle can
be calculated. Based on the result, it is found that Revivehas the highest
concentration of citric acid while Pop has the lowest concentration of
citric acid.
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1.0 INTRODUCTION
1.1 THEORY
Acids are added to a variety of food and beverages and contribute
significantly to their taste. Soft drinks often contain varying quantities of
several acids, giving sodas their tart flavor. Examples of these acids
added are citric acid and carbonic acid, which are found in sodas such as
7-UP and 100 Plus.
Citric acid is weak, polyprotic acid. It is both a natural and
artificially obtained acid. It is found naturally in living being as a key
component of the natural aerobic process of respiration. Citric acid was
first artificially produced in 1784 from lemon juice, by Karl Wilhelm
Scheele. It can also be obtained through bio-technology processes for
industrial purposes by fermenting the citrus glucose, sucrose or molasses
in combination with the fungus called Aspergillus niger.
(http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-
effects/?id=900)
1.2 LITERATURE REVIEW
Based on European Citric Acid Manufacturers Associations
(ECAMA's) experience, the use of citric acid and citrates in beverage and
soft drink applications reflects levels commonly found in natural fruits.
Typical additions of 0.25 to 0.4% of CITRIC ACID are used to enhance or
impart tangy flavours and chelate metal ions to improve product storage
together with flavour and colour stabilizations. Likewise sodium citrate at
0.1% can offer a cooling saline taste as well as providing buffering
http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-effects/?id=900http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-effects/?id=900http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-effects/?id=900http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-effects/?id=900http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-effects/?id=900http://www.veria.com/wellness/healing/citric-acid-benefits-uses-side-effects/?id=900 -
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capacity to stabilize pH hence aiding Carbon Dioxide retention.
(http://www.ecama.org/Reports/Softdrinks.doc\)
1.3 PROBLEM STATEMENT
Citric acid is the most frequently used preservative and additive in
the world today. It creates an acidic environment that is not favorable for
bacterial and microbes to carry out essential living processes. Besides,
citric acid contributes to many health benefits, such as preventing kidney
stones, accelerating mineral absorption into the body, treating sore throat
and nausea, helping in the regeneration of skin tissue and as an anti-
oxidant. However, there are some potential health effects in the
consumption of citric acid, which may cause allergic reaction, eye
irritation, gastrointestinal tract irritation with nausea, vomiting and
diarrhea. Furthermore, frequent intake of citrated beverages may cause
erosion of dental enamel and irritation of mucous membranes
(http://www.sciencelab.com/msds.php?msdsId=9923494). A study at the
University of Bristol, UK, has found that the increasing incidence of
enamel erosion was causally connected to the high amounts of citric acid
added to drinks and food (http://www.alive.com/articles/view/
17903/is_citric_acid_truly_safe). Therefore, it comes to our concern
whether the food and beverage we consume contain a high concentration
of citric acid.
1.4 OBJECTIVE
The objective of this project is to determine the concentration of
citric acid in soft drinks.
http://www.ecama.org/Reports/Softdrinks.doc/http://www.ecama.org/Reports/Softdrinks.doc/http://www.ecama.org/Reports/Softdrinks.doc/http://www.sciencelab.com/msds.php?msdsId=9923494http://www.sciencelab.com/msds.php?msdsId=9923494http://www.sciencelab.com/msds.php?msdsId=9923494http://www.alive.com/articles/view/%2017903/is_citric_acid_truly_safehttp://www.alive.com/articles/view/%2017903/is_citric_acid_truly_safehttp://www.alive.com/articles/view/%2017903/is_citric_acid_truly_safehttp://www.alive.com/articles/view/%2017903/is_citric_acid_truly_safehttp://www.alive.com/articles/view/%2017903/is_citric_acid_truly_safehttp://www.alive.com/articles/view/%2017903/is_citric_acid_truly_safehttp://www.sciencelab.com/msds.php?msdsId=9923494http://www.ecama.org/Reports/Softdrinks.doc/ -
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2.0 METHODOLOGY
In this project, samples of soft drinks are titrated against a
standard sodium hydroxide solution. Careful technique is adopted to
detect the endpoint when the reaction is complete. With the aid of an
indicator, the endpoint can be observed easily. The method used to carry
out titration between citric acid in soft drinks and sodium hydroxide
solution can be divided to two parts: preparation of a standard NaOH
solution and titration of the soft drinks.
(A) Preparation of a standard NaOH solution
1. 1.0g of NaOH is weighed and dissolved in beaker by using distilled
water. After that, the solution is made up to 250ml of 0.1mol dm-3NaOH
solution.
(B) Titration of soft drinks
1. The soft drink samples have been left flat for several days in advance
to assure it is decarbonized.
2. 10.00cm3of the soft drink is pipetted into 250ml conical flask and 2 to 3
drops of phenolphthalein are added into the soft drink.
3. The buret is filled with standard NaOH solution. The initial volume of
NaOH solution in the buret is recorded. NaOH solution is slowly added to
the soft drink until the first faint lasting pink colour appears. Once a
lasting pink colour has been reached, the final volume of NaOH from the
buret is recorded.
5. The molarity of the citric acid in the soft drink is calculated.
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6. Steps 3 to 5 are repeated three more times and the average molarity is
calculated.
7. From the average molarity of citric acid, the number of moles of citric
acid per can or bottle of soft drink is calculated.
8. Finally, the number of grams of citric acid per can or bottle of soft drink
is calculated.
9. Steps 1 to 8 are repeated for others soft drink samples.
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3.0 RESULTS
3.1 TABULATION OF DATA
Table 1: Titration of soft drink 1 (7-UP)
Rough 1 2 3
Volume of soft drink (cm ) 25.00 25.00 25.00 25.00
Final burette reading, NaOH (cm ) 21.00 31.10 41.25 40.00
Initial burette reading, NaOH (cm3) 10.70 21.00 31.10 29.80
Total volume, NaOH (cm ) 10.30 10.10 10.15 10.20
Average volume, NaOH (cm ) 10.15
Molarity of citric acid (mol dm- ) 0.0135 0.0135 0.0136
Average molarity of citric acid (mol dm- ) 0.0135
Average moles of citric acid per
can/bottle (mol) 4.39 10-3
Average grams of citric acid per
can/bottle (g) 8.42 10-1
All data are tabulated in the same way as shown in Table 1.
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3.2 CALCULATION
3.2.1 THEORY OF CALCULATION
Citric acid is a weak, polyprotic acid that can undergo
neutralization reaction with sodium hydroxide solution. The reaction
between citric acid and sodium hydroxide solution is shown below:
H3C6H5O7(aq) + 3 NaOH (aq) 3 H2O (l) + Na3C6H5O7(aq)
The molarity of citric acid in a soft drink can be calculated by using the
formula:
, where M is molarity and V is volume.
The average number of moles of citric acid per can or bottle can be
calculated by using the formula:
The average grams of citric acid per can or bottle can be calculated by
using the formula:
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3.2.2 EXAMPLE OF CALCULATION
Calculation on soft drink 1 (7-UP):
Similar calculations are carried out for the other soft drinks.
Calculation on the consecutive difference of citric acid per can or bottle of
soft drinks: (Between Pop and Mountain Dew)
Similar calculations are carried out for the other consecutive soft drinks.
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3.2.3 SUMMARY OF CALCULATION
Table 2: Ascending concentration of citric acid per can or bottle
Soft drinks
Average number of moles
(mol)
Average grams
(g)
Pop 3.45 10- 6.61 10-
Mountain Dew 3.80 10- 7.30 10-
Ice-Cream
Soda 4.03 10-3
7.74 10-1
7-UP 4.39 10- 8.42 10-
100 Plus 5.00 10- 9.60 10-
Revive 5.20 10- 9.98 10-
Higher average number of moles and average number of grams of
citric acid per can or bottle indicates that the soft drink has higher
concentration of citric acid. Based on the results, Revivehas the highest
concentration of citric acid, followed by 100 Plus, 7-UP, Ice-Cream Soda,
Mountain Dewand Pop.
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Table 3: Consecutive difference in concentration of citric acid per
can/bottle of soft drinks
Soft drinks
Difference
Number of moles
(mol)Grams (g)
Pop0.35 10-3 0.69 10-1
Mountain Dew
Mountain Dew0.23 10-3 0.44 10-1
Ice-Cream Soda
Ice-Cream Soda0.36 10-3 0.68 10-1
7-UP
7-UP
0.61 10-3 1.18 10-1100 Plus
100 Plus0.20 10-3 0.38 10-1
Revive
Revive1.75 10-3 3.37 10-1
Pop
Average 3.50 10-4 6.74 10-1
The average difference in number of mols and grams between
consecutive soft drinks is small, thus indicating that all the soft drinks
have almost the same concentration of citric acid per can or bottle.
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3.3 DISCUSSION
In this project, the volume of sample of soft drinks used is same,
that is one can or bottle, which is 325cm
3
. It is assumed that only citric
acid and carbonic acid are present in the soft drinks chosen. Since
carbonic acid can be removed by releasing all carbon dioxide from the
soft drinks, the only acid present in the soft drinks chosen is assumed to
be citric acid.
Phenolphthalein is used as an indicator to determine the endpoint
of the titration. Phenolphthalein is pink in acidic solution and is colourless
in basic solution. Therefore, when the solution changes from colourless to
pink, the acid-base reaction is said to be complete.
The readings of each titration are prone to random errors such as
observational errors of determining the endpoint of titration which will
result in the addition excess base to the acid. This causes inaccuracy of
result that might not be the true value of the volume of base that has
reacted. The mistakes can be reduced by titrating slowly and shaking the
conical flask to ensure that no excess base is added. Furthermore, error
might have occurred when reading the meniscus level of titre. The
titration for each sample is repeated a few times to improve the accuracy
of results by taking the average value.
Based on the results, it is found that all the soft drinks chosen have
almost the same concentration of citric acid per can or bottle. Revivehas
the highest concentration of citric acid per can or bottle while Pophas the
lowest concentration of citric acid per can or bottle.
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4.0 CONCLUSION
The concentration of citric acid in soft drinks can be determined by
using acid-base titration. Revive has the highest concentration of citric
acid per can or bottle, followed by 100 Plus, 7-UP, Ice-Cream Soda and
Mountain Dew. Pop has the lowest concentration of citric acid per can or
bottle. The difference between the highest concentration of citric acid per
can or bottle, Revive, and the lowest concentration of citric acid per can
or bottle, Pop, is 1.75 10-3mol or 3.37 10-1g, which is not significant in
comparison. There is a small difference in the concentration of citric acid
between the other types of soft drink, which has the average difference of
3.5 10-4 mol or 6.74 10-1g, indicating that all these soft drinks have
almost the same concentration of citric acid per can or bottle.
4.1 SUGGESTION
Studies have found that over dosage of citric acid will cause side
effects. (http://www.livestrong.com/article/152574-effects-of-citric-acid-on-
people/) However, there is limited study on the recommended daily
allowance of citric acid and the amount of citric acid that will cause side
effects. Therefore, further investigation on the recommended daily
allowance of citric acid and the amount of citric acid that is safe to be
consumed should be carried out in the future research. This is to ensure
that the consumption of citric acid will not bring side effects to the
consumer.
http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/ -
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5.0 REFERENCES/BIBLIOGRAPHY
http://www.alive.com/articles/view/17903/is_citric_acid_truly_safe
http://www.sciencelab.com/msds.php?msdsId=9923494
http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/
http://www.veria.com/healing/citric-acid-benefits-uses/?id=900
http://www.flavours.asia/uploads/7/9/8/9/7989988/titration.pdf
http://www.ecama.org/Reports/Softdrinks.doc
Tan Yin Toon, Loh Wai Leng, Lim Ming Hui, Ho Sook Chee, Ace Ahead
STPM Text Chemistry First Term, Oxfod Fajar Sdn. Bhd., 2012.
http://www.alive.com/articles/view/17903/is_citric_acid_truly_safehttp://www.alive.com/articles/view/17903/is_citric_acid_truly_safehttp://www.sciencelab.com/msds.php?msdsId=9923494http://www.sciencelab.com/msds.php?msdsId=9923494http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.veria.com/healing/citric-acid-benefits-uses/?id=900http://www.veria.com/healing/citric-acid-benefits-uses/?id=900http://www.flavours.asia/uploads/7/9/8/9/7989988/titration.pdfhttp://www.flavours.asia/uploads/7/9/8/9/7989988/titration.pdfhttp://www.ecama.org/Reports/Softdrinks.dochttp://www.ecama.org/Reports/Softdrinks.dochttp://www.ecama.org/Reports/Softdrinks.dochttp://www.flavours.asia/uploads/7/9/8/9/7989988/titration.pdfhttp://www.veria.com/healing/citric-acid-benefits-uses/?id=900http://www.livestrong.com/article/152574-effects-of-citric-acid-on-people/http://www.sciencelab.com/msds.php?msdsId=9923494http://www.alive.com/articles/view/17903/is_citric_acid_truly_safe