A CHEMISTRY PROJECT“STUDY OF THE OXALATE ION CONTENT IN GUAVA FRUIT”Submitted in the partial Fulfilment of the requirement for AISSCE 2012-2013 .

INTRODUCTION OBJECTIVE OF THE PROJECT REQUIREMENTS THEORY CHEMICAL EQUATIONS PROCEDURE PRECAUTIONS OBSERVATIONS CALCULATIONS CONCLUSION BIBLIOGRAPHYS

BY NAIRITA MUKHOPADHYAY class xii c roll 2411/22/2012

CONTENTS

 INTRODUCTION

OBJECTIVE OF THE PROJECT

REQUIREMENTS  THEORY  CHEMICAL EQUATIONS  PROCEDURE  PRECAUTIONS  OBSERVATIONS  CALCULATIONS

CONCLUSION  BIBLIOGRAPHY

STUDY OF OXALATE ION CONTENT INGUAVA FRUIT

INTRODUCTION Guava is sweet, juicy and light or dark green coloured fruit. It iscultivated in all parts of India. When ripe it acquires yellow colourand has penetrating strong scent. The fruit is rich in vitamin C andminerals. It is a rich source of oxalate and its content in the fruitvaries during different stages of ripening.Guava fruit, usually 4 to 12 cm long, are round or oval dependingon the species. The outer skin may be rough, often with a bittertaste, or soft and sweet. Varying between species, the skin can beany thickness, is usually green before maturity, but becomes yellow,maroon, or green when ripe.Guava fruit generally have a pronounced and typical fragrance,similar to lemon rind but less sharp. Guava pulp may be sweet orsour, off-white ("white"

guavas) to deep pink ("red" guavas), with theseeds in the central pulp of variable number and hardness, againdepending on species.

WHAT IS OXALATE?

Oxalate is an organic acid, primarily found in plants, animals andhumans. It is not an essential molecule and is excreted from ourbody in an unchanged form. Our body either produces oxalate on itsown or it converts other molecules like vitamin C to oxalate. Externalsources like the foods we eat also contribute to the accumulation of oxalate in our body. The oxalate present in the body is excreted inour urine as a waste. Too much of oxalate in our urine, results in amedical condition called as hyperoxaluria, commonly referred to askidney stones. Diet is looked upon as a preventive measure inaddition to medicines to treat kidney stones. Read more on whatcauses kidney stones

OBJECTIVE OF PROJECT

In this project, we will learn to test for the presence of oxalate ions inthe guava fruit and how its amount varies during different stages of ripening.

REQUIREMENTS

MATERIALS REQUIRED

100 ml Measuring Flask Pestle and Mortar Beaker Titration Flask 

CHEMICALS REQUIRED

Dilute H2SO4, KMnO4 solution

THEORYOxalate ions are extracted from the fruit by boiling pulp with dil.H2SO4. Then oxalate ions are estimated volumetrically by titrating thesolution with standard KMnO4solution.Titration is a common laboratory method of quantitative chemicalanalysis that is used to determine the unknown concentration of aknown reactant. Because volume measurements play a key role intitration, it is also known as volumetric analysis. A reagent, calledthe titrant or titrator, 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 acalibrated burette or chemistry pipetting syringe to add the titrant, itis possible to determine the exact amount that has been consumedwhen the endpoint is reached. The endpoint is the point at which thetitration is complete, as determined by an indicator (see below). Thisis ideally the same volume as the equivalence point—the volume of added titrant at which the number of moles of titrant is equal to thenumber of moles of analyte, or some multiple thereof (asin polyprotic acids). In the classic strong acid-strong base titration,the endpoint of a titration is the point at which the pH of thereactant is just about equal to 7, and often when the solution takeson a persisting solid colour as in the pink of phenolphthalein indicator

CHEMICAL EQUATIONS

Molecular Equations

2KMnO4+ 3H2 SO4= K2 SO4+ 2MnSO4+ 2H2 O + 4[O]

PROCEDURE

1. Weigh 50.0g of fresh guava and crush it to a fine pulp using pestle-mortar. 2.Transfer the crushed pulp to beaker and add about 50 ml dil. H2SO4 to it .

3. Boil the contents for about 10 minutes

4.cool and filter the contents in a 100 ml measuring flask. Make thevolume upto 100 ml by adding distilled water.

5. Take 20 ml of the solution from the measuring flask into a titration flaskand add 30 ml of dilute sulphuric acid to it.

6. Heat the mixture to about 60degree C and titrate it against N/20 KMnO4 solutiontaken in a burette.The end point is appearance

of light-pinkcolour permanent. 7. Repeat the above experiment with 50.0 g of 1, 2 and 3 days old guavafruit.

 

PRECAUTION

1.KMnO4solution is always taken in theburette.

 2.Avoid the use of burette having a rubber tap as KMnO4 attacks rubber.

 3.In order to get some idea about the temperature of the solution touchthe flask to the back side of your hand. When it becomes unbearable totouch, the required temperature is reached.

 4.Add about an equal volume of dil. H2SO4 to the guava extract to be titrated (say a full test tube) before adding KMnO4

.5. Read the upper meniscus while taking burette reading withKMnO4 solution.

6. In case, on addition of KMnO4 a brown ppt. appears, this shows that either H2SO4 has not been added or has been added ininsufficient amount. In such a case, throw away the solutionand titrate again. 7.The concentration of oxalate ion obtained from the filtrate isunfavourably high. If the titration is carried with concentratedfiltrate, the scale of the burette is out of scope in regard to theconcentration of the oxalate ion. So diluting the concentratedfiltrate to an appropriate proportion and titrating it withKMnO4 and

estimating the end point will make it favourable.After estimating the end from the diluted solution, the originalconcentration of the concentrated filtrate can be calculated by multiplying the concentration the estimated filtrate with the factor by which it was diluted.

OBSERVATIONS

Weight of guava fruit taken each time = 50.0 g Volume of guava extract taken in each titration = 20.0 ml

Normality of KMnO4 solution =1/20 N

 

 

 

CALCULATIONS

For fresh guavaN1 V1=N2 V2

N1 x 10 =1/20 x x

 Normality of oxalate, N1= x/200 Strength of oxalate in fresh guava extract= Normality x Eq. mass of oxalate ion= x/200 x 44 g/litre of the diluted extract.

Similarly, calculate the strength of oxalate in 1, 2 and 3 days old guavaextract and interpret the result.

CONCLUSION

The concentration of the oxalate ion increases with increase with ripening.

BIBLIOGRAPHY1. INDIAN INSTITUTE OF APPLIED SCIENCE:http://www.ias.ac.in/currsci/aug102001/248.pdf  2. www.wikipedia.org 3.Comprehensive Practical Chemistry for Class Xii