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1) For raw guavaN1V1 = N2V2
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N1 x 10 = (1/10) x132
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1/10 x Normality of oxalate = ( x /100) = strength of oxalate in freshguava extract = normality x Eq. mass of oxalate ion= 1.32/100 x 44g/litre of diluted extract= 0.581 g L
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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
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) For ripened guavaStrength of oxalate in fresh guava extract= ( 1.39/100) x 44g/litre of diluted extract=0.612g L
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(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

The content of oxalate ions in guava was found to be 59.67 per cent, which isclose 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:
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www.google.com
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www.wikipedia.com
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www.reader.google.com
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www.labs.google.com
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www.quora.com 2. Practical Chemistry by Laxmi Publications.3. The Family Encyclopedia by Dorling Kindersley.

There should be no parallax while taking measurements.

Spillage of chemicals should be checked.

Avoid the use of burette having a rubber tap as KMnO
4
attacks rubber.In order to get some idea about the temperature of the solution touch the flask with the back side of your hand. When it becomesunbearable to touch, the required temperature is reached. Add about an equal volume of dil. H
2
SO
4
to the guava extract to be titrated (say a full test tube) before adding KMnO
4
.Read the upper meniscus while taking burette reading with KMnO4solution.In case, on addition of KMnO
4
a brown ppt. appears, this shows thateither H
2
SO
4
has not been added or has been added in insufficientamount. In such a case, throw away the solution and titrate again.
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 KMnO
4
solution was
(1/10).4.

END POINT:
Colour Changes to pink
GuavaSolution

BurettereadingInitial

FinalReading

Volume ofKMnO4

ConcurrentReading

Raw

150 18 132136.06emi-ripened

150 13 137Ripened

150 10.8 139.2