A water sample is not alkaline to phenolphthalein end point, however 100ml of the sample, on titration with N/50 HCl, required 16.9ml to obtain the end point using methyl orange as indicator. What is the type of alkalinity present in given water sample
Answers
Here diacidic base is present which give two end point one with phenalphthein and second with methy orange
For phenolphthalein end point-
\frac{1}{2}\ Meq\ of\ Diacidic\ base = Meq.\ of\ of \ 8ml \ \frac{N}{50}\ HCl
2
1
Meq of Diacidic base=Meq. of of 8ml
50
N
HCl
=\frac{1\times 8}{50\times1000}=\frac{1}{6225}\ Meq\\
50×1000
1×8
=
6225
1
Meq
Meq.\ of\ Diacidic\ base=2\times Meq.\ of\ HCl=\frac{2}{6225}\ Meq.Meq. of Diacidic base=2×Meq. of HCl=
6225
2
Meq.
For methyl orange end point-
Meq.\ of\ monoacidic\ base\ formed=Meq.\ of\ 1ml of\ extra\ HCl\ usedMeq. of monoacidic base formed=Meq. of 1mlof extra HCl used
=\frac{1\times1}{50\times 1000}=\frac{1}{50000\ Meq.}=
50×1000
1×1
=
50000 Meq.
1
Normality of diacidic alkalinity present in 100 ml water = \frac{2\times 1000}{6225\times 100}=\frac{20}{6225}=\frac{4}{1245}\ N
6225×100
2×1000
=
6225
20
=
1245
4
N