This PDF contains the project work for Chemistry on the topic "Presence of oxalate ions in Guava in different stages of ripening".

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Presence
Presence
Presence
Presence of
of
of
of
Oxalate
Oxalate
Oxalate
Oxalate ions
ions
ions
ions in
in
in
in
Guava
Guava
Guava
Guava
A
A Chemistry
Chemistry Investigatory
Investigatory
Project
Project
Punit
Punit
Punit
Punit
Punit
Goswami
Goswami
Goswami
Goswami
Goswami
2012
2012

2. P
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Certificate
Certificate
Certificate
Certificate
his is to certify that Punit Goswami of class 12
th
B
has satisfactorily completed the project in chemistry
on Presence of Oxalate ions prescribed by the
AISSCE course in the academic year 2012-13. I have
examined the project and hereby accord my approval of it
as a study carried out and presented in the manner
required for its acceptance. This does not necessarily
endorse or accept every statement made or opinion
expressed or conclusion drawn, but only signifies the
acceptance of the project for the purpose it is submitted
for.
Mr. P.N. Yadav Dr. Shalini Dikshit
PGT Chemistry Principal, K.V. Manauri
Acknowledgement
Acknowledgement
Acknowledgement
Acknowledgement
I hereby acknowledge my deep sense of gratitude
and indebtedness to Mr P.N. Yadav, PGT (Chemistry) whose
immense help, genius guidance, encouragement, necessary
suggestions, initiations, enthusiasm and inspiration made this
T

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work a master art and a joint enterprise.
Contents
Contents
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

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To study the
presence of oxalate
ions in guava fruit at
different stages of ripening.
Introduction
Introduction
Introduction
Introduction
Introduction
Introduction
uava is a common sweet fruit found in India
and many other 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.
Guavas have a pronounced and typical fragrance, similar to lemon rind but less
in strength.
What
What
What is
is
is oxalate?
oxalate?
oxalate?
t 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. 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
G
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AIM
AIM
AIM
AIM

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measure in addition to medication to treat kidney stones.
Theory
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.
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
O
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indicator.
Requirements
Requirements
(A) Apparatus
100 ml measuring flask Pestle & Mortar Beaker
Burette
Funnel Weighing machine Filter
Papers

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(B) Chemicals
1. dil. H2SO4 2. (N/10) KMnO4 solution
(C) Guava fruits at different stages
of ripening.
Chemical
Chemical
Chemical
Chemical
Equations
Equations
Equations
Equations
Molecular
Molecular
Molecular
Molecular Equations
Equations
Equations
Equations
2KMnO
2KMnO4
4+
+ 3H
3H2
2SO
SO4
4 
 K
K2
2SO
SO4
4+
+ 2MnSO
2MnSO4
4+2H
+2H2
2O
O +
+ 4[O]
4[O]
HOOC-COOH.2H
HOOC-COOH.2H2
2O
O +
+ [O]
[O] 60
600
0
C
C –
– 70
700
0
C
C 2CO
2CO2
2+
+ 2H
2H2
2O
O x
x 5
5
3KMnO
3KMnO4
4+
+ 3H
3H2
2SO
SO4
4+
+5
5 HOOC-COOH.2H
HOOC-COOH.2H2
2O
O 

K
K2
2SO
SO4
4+
+ 2MnSO
2MnSO4
4+
+ 18H
18H2
2O
O +
+ 10CO
10CO2
2
Ionic
Ionic
Ionic
Ionic Equations
Equations
Equations
Equations
MnO
MnO4-
4-
+16H
+16H+
+
+
+ 5e
5e-
-

 Mn
Mn2+
2+
+
+ 4H
4H2
2O
O x
x 2
2
C
C2
2O
O4
4 
 2CO
2CO2
2+
+ 2e
2e-
-
x
x 5
5
2MnO
2MnO4-
4-
+
+ 16H
16H+
+
+
+ 5C
5C2
2O
O4
4
2
2-
-

 2Mn
2Mn2+
2+
+8H
+8H2
2O
O +
+ 10CO
10CO2
2

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Procedure
Procedure
Procedure
Procedure
(1) Weighed 50 g of fresh guava and crushed it to a fine pulp using
pestle and mortar.
(2) Transferred the crushed 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
Precautions
Precautions
Precautions
1.
1.There should be no parallax while taking measurements.
2.
2.Spillage of chemicals should be checked.
3.
3. Avoid the use of burette having a rubber tap as KMnO4attacks
rubber.
4.
4. In order to get some idea about the temperature of the solution
touch the flask with the back side of your hand. When it becomes
unbearable to touch, the required temperature is reached.

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5.
5. Add about an equal volume of dil. H2SO4 to the guava extract to
be titrated (say a full test tube) before adding KMnO4.
6.
6. Read the upper meniscus while taking burette reading with
KMnO4 solution.
7.
7. In case, on addition of KMnO4 a brown ppt. appears, this shows
that either H2SO4 has not been added or has been added in
insufficient amount. In such a case, throw away the solution and
titrate again.
Observations
Observations
Observations
Observations
1. Weight of the guava fruit for each time was 50 g.
2. Volume of guava extract taken for each titration was 20 ml.
3. Normality of KMnO4 solution was (1/10).
4. END POINT: Colour Changes to pink
Guava
Solution
Burette
reading
Initial
Final
Reading
Volume of
KMnO4
Concurrent
Reading
Raw 150 18 132
136.06
Semi-
ripened
150 13 137
Ripened 150 10.8 139.2
Calculations
Calculations
1) For raw guava
N1V1 = N2V2
N1 x 10 = (1/10) x132

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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
= 0.581 g 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
= 0.603 g L
-1
3) For ripened guava
Strength of oxalate in fresh guava extract
= ( 1.39/100) x 44g/litre of diluted extract
= 0.612 g L
-1
Results
Results
(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 = 1.39 ml
(b) The strength of oxalate ions of;
(i) Fresh guava solution is = 0.58 ml
(ii) Semi-ripened guava is = 0.60 ml
(iii) Ripened guava is = 0.61 ml

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Conclusions
Conclusions
Conclusions
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.
Bibliography
Bibliography
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.