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Compare the efficient pH range of different indicator using the model

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Posobie English for Masters of Chemistry

Indicator pH range Color acid solution Color base solution

Compare the efficient pH range of different indicator using the model.
Model:
Methyl orange is more acidic than litmus.
Phenol red is less basic than alizarin yellow.
pH INDICATORS
A pH indicator is an indicator used in the titration of an acid and a base which is also
called a neutralization titration. A pH indicator indicates the neutralization point or end point
or equivalence point by a change in color which is distinct.
pH Indicator List
The different indicators and their efficient range of pH are given below.
Indicator
pH range Color acid solution Color base solution
Cresol blue
1.2 - 1.8
Red
Yellow
Thymol blue
1.2 - 2.8
Red
Yellow
Methyl yellow
2.9 - 4.0
Red
Yellow
Methyl orange
3.1 - 4.4
Pink
Yellow
Methyl red
4.2 - 6.3
Red
Yellow
Litmus
5.0 - 8.0
Red
Blue
Bromothymol blue 6.0 - 7.6 Yellow
Blue
Phenol red
6.4 - 8.2
Yellow
Red
Thymol blue (base) 8.1 - 9.6
Yellow
Blue
Phenolphthalein
8.3 - 10.0 Colorless
Purple
Thymolphthalein
8.3 - 10.5 Colorless
Blue
Alizarin yellow
10.1 - 12.0 Blue
Yellow
Nitramine
10.0 - 13.0 Colorless
Orange/brown
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Universal pH Indicator
A universal indicator is the one which can give color changes differently at a small
range of pH variations. Most common composition of a universal indicator is methanol,
propan-1-ol, sodium salt of phenolphthalein, sodium salt of methyl red, bromothymol blue
monosodium salt, and phenol. This is applied on strips of cellulose paper for dip test or used
as aqueous solution if used in a titration. The color changes when the universal indicator is
used.

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