STUDY OF THE PRESENCE OF OXALATE IONS IN GUAVA FRUIT AT
DIFFERENT STAGE OF RIPPENING
Submitted by
AAHIL ARSHAD.S
(Reg No: M/2/21/55183/0001)
CLASS :
XII-ZINNIA
Under the Guidance and Supervision of
MrANOOP P.GEORGE Msc.CHEMISTRY,
Subject Teacher of Chemistry,
DEPARTMENT OF CHEMISTRY
SRRI SPK PUBLIC SENIOR SECONDARY SCHOOL
(Affiliated to CBSE, Delhi)
Kadachanallur-638008
2020-2021
CERTIFICATE
This is to certify that AAHIL ARSHAD.S (Registration No: M/2/21/55183/0001) student of
class XII-ZINNIA has successfully completed the research on the below mentioned project
under the guidance of Mr.ANOOP P.GEORGE Msc.CHEMISTRY., during the year 2020-21
in partial fulfillment of Chemistry practical examination conducted by AISSCE, New Delhi.
Signature of
Internal Examiner
Date:
Signature of
External Examiner
Principal
ACKNOWLEDGEMENT
In the accomplishment of this project successfully, many people have best owned
upon me their blessings and the heart pledged support, this time I am utilizing to thank all
the people who have been concerned with project.
Primarily I would thank god for being able to complete this project with success. Then I
would like to thank my principal and chemistry teacher whose valuable guidance has been the
ones that helped me patch this project and make it full proof success his suggestions and his
instructions has served as the major contributor towards the completion of the project.
Then I would like to thank my parents and friends who have helped me with their valuable
suggestions and guidance has been helpful in various phases of the completion of the project.
Contents
o Aim of the project
o Introduction
o Theory
o Requirements
o Chemical Equations
o Procedure
o Precautions
o Observations
o Calculations
o Conclusions
AIM
To study the presence of oxalate
ions in guava fruit at different
stages of ripening.
G
uava is a common sweet fruit found in India and many
places around the world. Guavas are plants in the
Myrtle family (Myrtaceae) genus Psidium (meaning
"pomegranate" in Latin), which contains about 100 species
of tropical shrub. On ripening it turns yellow in color. Rich
in vitamin C, this fruit is a rich source of oxalate ions
whose content varies during the different stages of ripening.
other
Guavas have a pronounced and typical fragrance, similar to
lemon rind but less in strength.
What is oxalate?
I
t is a carboxylic acid, primarily found in plants and animals. It is not an essential
moleculeand is excreted fromour body, unchanged. Our body either produces
oxalate on its own or converts other molecules like Vitamin C to oxalate. External
sources like food also contribute to the accumulation of oxalate in our body. The oxalate
present in the body is excreted in the form of urine as waste. Too much of oxalate in our
urine results in
a medical condition called
hyperoxaluria, commonly
referred to as kidney stones.
Diet is looked upon as a
preventive measure in
addition to
medication to treat
kidney stones.
O
Theory
xalate ions are extracted from
the fruit by boiling pulp with
dilute H2SO4. The oxalate ions
are estimated volumetrically, by
titrating the solution with
KMnO4 solution. A reagent,
called the titrant, of a known
concentration (a standard
solution) and volume is used to
react with a solution of the analyte or
titrand, whose concentration is not
known. Using a calibrated burette or
chemistry pipetting syringe to add the
titrant, it is possible to determine
the exact amount that has been consumed when the endpoint is reached. The
endpoint is the point at which the titration is complete, as determined by an
indicator. This is ideally the same volume as the equivalence point.
T
he volume of added titrant at which the number of moles of titrant is
equal to the number of moles of
analyte, or some multiple thereof (as in
polyprotic acids). In the classic strong
acid-strong base titration, the endpoint of a
titration is the point at which the pH of the
reactant is just about equal to 7, and often when
the solution takes on a persisting solid colour as in
the pink of phenolphthalein indicator.
Requirements
(A)Apparatus
100 ml measuring flask
Pestle & Mortar
Burette
Funnel
Beaker
Weighingmachine
(B) Chemicals
1. dil. H2SO4
(C) Guava fruits at different stages
of ripening.
Filter Papers
2. (N/10)
KMnO4
solution
Chemical Equations
Molecular Equations
Ionic Equations
Procedure
(1)Weighed 50 g of fresh guava and crushed it to a fine pulp using
pestle and mortar.
(2)Transferredthecrushed pulp to a beaker and added about 50 ml
dilute H2SO4 to it.
(3)Boiled the content for about 10 minutes. Cooled and filtered the
contents in a 100 ml measuring flask.
(4)Made up the volume 100 ml by adding ample amount of distilled
water.
(5)Took 20 ml of the solution from the flask and added 20 ml of
dilute sulphuric acid to it.
(6)Heated the mixture to about 600 C and titrated it against (n/10)
KMnO4 solution taken in a burette till the end point had an
appearance of pink colour.
(7) Repeated the above experiment with 50 g of 1day, 2 day and 3 day
old guava fruits.
Precautions
1. There should be no parallax while taking measurements.
2. Spillage of chemicals should be checked.
3. Avoid the use of burette having a rubber tap as
KMnO4attacksrubber.
4. In order to get some idea about the temperature of the
solution touchthe flask with the back side of your hand. When
it becomes unbearable totouch, the required temperature is
reached.
5. Add about an equal volume of dil. H2SO4to the guava extract
tobe titrated (say a full test tube) before adding KMnO4.
6. Read the upper meniscus while taking burette reading
withKMnO4 solution.
7. In case, on addition of KMnO4a brown ppt. appears, this
showsthat either H2SO4has not been added or has been added
ininsufficient amount. In such a case, throw away the
solutionand titrate again.
Observations
1.
2.
3.
4.
Weight of the guava fruit for each time was 50 g.
Volume of guava extract taken for each titration was 20 ml.
Normality of KMnO4 solution was (1/10).
END POINT: Colour Changes to pink
Guava
Burette
Final
Volume of
Concurrent
Solution
reading
Reading
KMnO4
Reading
Initial
Raw
150
18
132
136.06
Semi-ripened 150
13
137
Ripened
150
10.8
139.2
1)
For raw guava
N1V1 = N2V2
N1 x 10 = (1/10) x132
1/10 x Normality of oxalate = (x/100) = strength of oxalate in fresh
guava extract= normality x Eq. mass of oxalate ion
= 1.32/100 x 44g/litre of diluted extract
=0.581g L-1
2)
For semi ripened guava (1 day old).
Strength of oxalate in one day old guava extract
= (1.37 /100) x 44g/litre of diluted extract
=0.603g L-1
3)
For ripened guava
Strength of oxalate in fresh guava extract
44g/litre of diluted extract
=
0.612g L-1
= ( 1.39/100) x
(a) The normality of oxalate ions of;
(i) Fresh guava solution is = 1.32 ml
(ii) Semi-ripen guava solution is = 1.37 ml
(iii) Ripened guava solution is = 1.39ml
(b)The strength of oxalate ions of;
(i) Fresh guava solution is =0.58ml
(ii) Semi-ripened guava is =0.60 ml
(iii) Ripened guava is = 0.61 ml
The content of oxalate ions in guava was found to be 59.67 per cent,
which is close to the literature value of 60 percent.
It was also noticed that the content of oxalic ions grows with ripening
of guava.
1. Search engines used:
 www.google.com
 www.wikipedia.com
 www.reader.google.com
 www.labs.google.com
 www.quora.com
2. Practical Chemistry by Laxmi Publications.
3. The Family Encyclopedia by Dorling Kindersley.