determination of the concentration of citric acid using acid base titration

5/26/2018 Determination of the Concentration of Citric Acid Using Acid Base Titratio...

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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:



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.


http:///reader/full/determination-of-the-concentration-of-citric-acid-using-acid6

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:


http:///reader/full/determination-of-the-concentration-of-citric-acid-using-acid

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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

determination of the concentration of citric acid using acid base titration

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