Study Presence of Oxalate Ions in Guava at Ripening Stages
1. Chemistry
Project Report
On
“Study the presence of oxalate ions in
guava fruit at different stages of
ripening”
Session: 2015-16
Under Supervision of Submitted by
Ms. Poonam Chauhan Rajiv Verma
Lecturer in Chemistry Roll No……………
Class XII (Medical)
3. CERTIFICATE
This is to certify that the project titled “Study the presence of oxalate
ions in guava fruit at different stages of ripening”, has been undertaken by
Rajiv Verma, Roll No. a student of XII (Medical).
This project has been carried out as a part of Chemistry projects as
prescribed by the Central Board of Secondary Education. This work is done
by candidate’s own efforts.
Ms. Poonam Chauhan
Lect. in Chemistry
4. ACKNOWLEDGE MENT
I express my deep sense of gratitude to Ms. Poonam Chauhan,
Lecturer of Chemistry, Maharana Pratap Public School, Kurukshetra for her
inspiration, valuable guidance and constant encouragement in the
completion of this project. Without her it would have been an impossible
task for me. I have put my sincere effort to make this project interesting. I
have fully consulted all the available books on this subject and I am thankful
to esteemed authors
Rajiv Verma
Class 10+2
Medical
Roll No.
5. Introduction
Guava is mainly a winter fruit. It has many medicinal
properties and cultivated in almost all parts of India. Approximate
composition of this fruit is
Constituent % Amount
Water 76.10
Proteins 1.50
Fats 0.20
Calcium 0.01
Phosphorus 0.04
Vitamin 0.30
Organic matter 14.50
Guava fruit contains maximum amount of Vitamin C after
‘Amla’. But amount of Vitamin C decreases with the ripening of
the fruits. Probably vitamin C gets converted to oxalate with
ripening of the fruit. Thus, amount of oxalate in the fruit may be a
reflection on the amount of vitamin C in it and its detennination,
therefore, makes an important study.
6. Objective:-
Determination of the oxalate ions in guava fruit at different
stages of its ripening.
Theory:-
Oxalate content of the fruit is made to go into solution by
boiling its pulp with distilled water and its amount in the solution
is determined by redox titration using potassium permanganate
solution.
Apparatus:
Pestle and mortar, beakers, 20ml measuring flask, funnel,
burette, pipette, conical flask, wire gauze. iron stand, tripod stand
and knife.
7. Chemicals.
0.05N KMnO4 solution, dil. H2 SO4 distilled water fully
riped, semi-riped and raw guava.
Procedure.
(i) Take one fully riped guava and peel off its skin. Weigh 25g
of this.
(ii) Make very small pieces of this with the help of a knife and
crush these in clean pestle and mortar.
(iii) Transfer the pulp so obtained into a 250 mL beaker. Wash
the pestle and mortar well with about 100 mL of distilled
water and transfer the washings also into the beaker.
(iv) Boil the contents of the beaker for about 10 minutes. Cool
and filter through a funnel. Collect the filtrate in a 250 mL,
measuring flask. Make the volume upto the mark i.e. 250 mL
by adding distilled water. Label the flask as riped guava
solution.
8. (v) Similarly, prepare 250 mL solution of 25g semi-riped and
raw guava.
(vi) Now, pipette out 25 mL of solution from one of the flask into
a conical flask. Add 20 mL of dilute sulphuric acid to it.
Warm the flask to about 60°C and titrate it with 0.05 N
KMnO4 solution until colour of the solution just changes to
permanent pink. Repeat the experiment with same solution
till three concurrent readings are obtained.
(vii) Similarly, find out the amount of 0.05 N potassium
permanganate solution required for titration in the other two
guava solutions.
(viii) Compare the three titre values i.e. volume of KMnO4
consumed for 25 mL of the three guava solutions. The guava
solution which consumes maximum volume of the
permanganite solution contains maximum oxalate ions.
9. Precautions:-
(i) Do not mix the three fruits or their solutions.
(ii) Boil the crushed fruit with equal amount of water and for the
same length of time in all the three cases.
(iii) Wash the pestle and mortar well before using for the other.
(iv) Weighing should be done accurately.
10. Observations:
Normality of the KMnO4 solution 0.05N
End point Colourless to pink
Volume of the guava solution taken each time for titration 25 rnL
Guava
solution
Burette readings Volume of the
KMnO4 used
in mL
Concurrent
reading in
mL
Initial Final
Riped
Guava …………. …………. ……………….. x1
Semi-riped
Guava …………. …………. ……………….. X2
Raw
Guava …………. …………. ……………….. X3
(The sample having the highest titre value has the maximum amount of
oxalate)
Conclusion:-
The amount of oxalate ions…………… with the ripening of
