This document describes an investigatory chemistry project analyzing the oxalate ion content in guava at different stages of ripening. The student measures the oxalate ion concentration in fresh guava, 1-day old guava, 3-day old guava, and 1-week old guava by titrating guava pulp solutions against a potassium permanganate solution. The results show that the oxalate ion content increases as the guava ripens, with the highest concentration measured in 1-week old guava. Through this project, the student determines that guava fruit contains high amounts of oxalate ions and that the percentage increases with ripening.
2. BONAFIDE CERTIFICATE
This is to certify that Nandan Ramesh , student
of class XII A, PSBB Learning Leadership Academy
has successfully completed his research on the
project “Analysis of Oxalate Ion in Guava” ,
under the guidance of subject teacher, Mrs.
Anjali Joshi during the academic year 2020-2021
in partial fulfillment of the chemistry practical
examination conducted by CBSE.
External Examiner
Teacher In-Charge School Principal
Seal of Institution
3. ACKNOWLEDGEMENT
I would like to thank our school’s
principal Mrs. Mahalaxmi Kumar and
Management for enabling the required
infrastructure/technology and
providing continuous support during
the course of this program.
I would like to express my sincere
gratitude to my Chemistry teacher Mrs.
Anjali Joshi and lab teachers Mrs. Usha
and Mrs. Deepthi for their vital support
and guidance even in the midst of the
Covid-19 lockdown, without which
successful completion of this project
would not have been possible.
Last but not the least, I heartfully thank
my family for providing all the help and
support that I needed while giving me
a positive and peaceful environment.
5. Precautions, Bibliography
Aim and Introduction
Apparatus Required and Theory
Results, Conclusions, Gallery
Procedure and Chemical Equations
Observations and Calculations
7. Guava is a common sweet fruit found
abundantly in India and many other
countries around the world. Guavas are
plants in the Myrtle family and contain
about 100 species of tropical shrubs. Green
when raw, on ripening they turn yellow.
Rich in vitamin C, this fruit is an excellent
source of oxalate ions whose content varies
during the different stages of ripening.
Guavas have a pronounced and typical
fragrance, similar to that of lemons but
much lesser in strength.The pulp inside
may be sweet or sour and vary from off-
white ("white" guavas) to deep pink ("red"
guavas). The seeds in the central pulp vary
in number and hardness, depending on the
species.
8. What is Oxalate Ion ?
• Oxalate (IUPAC: ethanedioate)
is the dianion with the formula
[ C2O4
2-
], also written as
[ (COO)2
2-
].
• It is a carboxylic acid, primarily
found in plants and animals. It
is not an essential molecule
and is excreted from our body,
unchanged.
• Our body either produces
oxalate on its own or converts
other molecules like Vitamin C
to oxalate. The oxalate present
in the body is excreted in the
form of urine as waste.
• Too much of oxalate in our
urine binds with minerals like
calcium in the digestive tract
resulting in a medical condition
called hyperoxaluria (kidney
stones).
• Oxalate also forms numerous
coordination compounds
where it is sometimes
abbreviated as (ox2-
).
9. 100 mL Conical Flask Pestle & Mortar 500 mL Beaker
Burette and Stand
Funnel
Weighting Machine Filter Paper
Dil. H2SO4 Solution KMnO4 Solution Guava Fruit at Different
Stages of Ripening
Pipette
Glazed White Tile
11. PROCEDURE
1) Crush the guava fruit to a fine pulp using a pestle and
mortar. Then weigh 50 g of fresh guava pulp on the
weighing machine.
2) Transfer the crushed pulp into a 500 mL beaker. Now,
add about 50 mL of dil. H2SO4 solution to the beaker and
boil the contents uniformly for about 2 minutes.
3) Cool and filter the contents into a 100 mL measuring
flask. Then, add distilled water to this flask until it reaches
the 100 mL mark.
4) Take 10 mL of guava pulp solution into a titration /
conical flask and add 5 mL of 1.0 M H2SO4 solution to it to
prevent the formation of any precipitate of manganese
dioxide during the course of the titration.
5) Heat the solution up to 50°– 60°C before titrating it
with potassium permanganate solution taken in the
burette. To increase the visibility of the colour change,
place the conical flask containing the solution to be
titrated over a white glazed tile kept below the nozzle of
the vertically fitted burette.
12. 6) Rinse and fill a clean burette with potassium
permanganate solution. Remove the air bubble, if any, from
the nozzle of the burette by releasing some solution through
it. The burette used in the permanganate titration must have
a glass stop cock as rubber is attacked by permanganate
ions.
7) Note the initial reading of the volume of permanganate
solution in the burette and add it in small volumes to the
hot oxalic acid solution while swirling the contents of the
flask gently.
8) The appearance of permanent
coloration in the titrand marks the completion of the
titration.
9) Repeat the titration till three concordant readings are
obtained. Since the solution of KMnO4 is of dark colour, the
upper meniscus should be considered for noting the burette
readings.
10) Repeat the above steps with 50 g of -
• 1-day old guava
• 3-day old guava
• Week (7-day) old guava
14. OBSERVATIONS
1) Burette Solution - 0.1 M Potassium Permanganate Solution
2) Pipette Solution - Guava Pulp Solution
3) Indicator - KMnO4 (self-indicator)
4) End Point - Colourless to permanent pale pink colour
5) Temperature - Room Temperature
6) Molar mass of KMnO4 - 158.034 g/mol
7) Molar mass of oxalate ion ( C2O4
2-
) - 88.02 g/mol
SIMPLE PROCEDURE
15. Volume of
std.
Solution
Burette Reading (mL)
Volume of
KMnO4
Initial
Reading
Final
Reading
10 mL 0 mL 15.2 mL 15.2 mL
10 mL 15.2 mL 30.3 mL 15.1 mL
10 mL 30.3 mL 45.4 mL 15.1 mL
CONCORDANT VALUE = 15.1 mL
OBSERVATION TABLES
Volume of
std.
Solution
Burette Reading (mL)
Volume of
KMnO4
Initial
Reading
Final
Reading
10 mL 0 mL 16.7 mL 16.7 mL
10 mL 16.7 mL 33.2 mL 16.5 mL
10 mL 33.2 mL 49.7 mL 16.5 mL
CONCORDANT VALUE = 16.5 mL
16. Volume of
std.
Solution
Burette Reading (mL)
Volume of
KMnO4
Initial
Reading
Final
Reading
10 mL 0 mL 21.4 mL 21.4 mL
10 mL 21.4 mL 42.7 mL 21.3 mL
10 mL 42.7 mL 64.0 mL 21.3 mL
CONCORDANT VALUE = 21.3 mL
Volume of
std.
Solution
Burette Reading (mL)
Volume of
KMnO4
Initial
Reading
Final
Reading
10 mL 0 mL 26.4 mL 26.4 mL
10 mL 26.4 mL 52.8 mL 26.4 mL
10 mL 52.8 mL 79.0 mL 26.2 mL
CONCORDANT VALUE = 26.4 mL
19. RESULTS
• Strength of Oxalate Ion in -
o Fresh Guava = 33.2276 g / L
o 1 Day Old Guava = 36.3082 g / L
o 3 Day Old Guava = 46.8706 g / L
o Week Old Guava = 58.0932 g / L
• Highest Strength of Oxalate Ion is
58.0932 g/L observed in 1 Week Old
Guava Extract.
• Lowest Strength of Oxalate Ion is
33.2276 g/L observed in Fresh Guava
Extract.
20. CONCLUSIONS
v It is evident that guava fruit
contains high amounts of
Oxalate Ions, about 60%.
v The percentage of Oxalate
Ions in guava fruit was clearly
found to be increasing as it
ripens.
v The amount of Oxalate Ions is
lowest when the fruit is fresh
and highest after 3-7 days from
when it is plucked.
22. v Always rinse the burette and the pipette with the
solutions to be taken in them.
v Never rinse the conical flask with the experimental
solutions.
v Remove the air gaps if any, from the burette.
v Never forget to remove the funnel from the burette
before noting the initial reading of the burette.
v No drop of the liquid should hang at the tip of the
burette at the end point and while noting reading.
v Always read the upper meniscus for recording the
burette reading in the case of all coloured solutions.
v Never use pipette and burette with a broken nozzle.
v Lower end of the pipette should always remain
dipped in the liquid while sucking the liquid.
v Do not blow out the last drop of the solution from
the jet end of the pipette.
v The strength of the solution must be calculated up
to the fourth decimal place.
v Do not forget to heat the mixture of guava pulp and
H2SO4 solutions between 50°–60° C while titrating it
against potassium permanganate.
PRECAUTIONS
