Analytical chemistry 2, Lecture4 (the indicators)

type of indicators which are weak organic acids or bases with high molecular weight and change their color according to pH:

• color indicator

• fluorescent indicator

• turbidity indicator

• external indicator

The iso-nitro acetyl p-amino azo-benzene indicator is:

• color indicator

• fluorescent indicator

• turbidity indicator

• natural indicator

the phenolphthalein color in acidic media is:

The Methyl Orange color in acidic media

the functional groups responsible for the color absorption of the indicator:

• auxochrome

• ionizable group

• chromophore

• groups with unshared electron

The pH range of the indicator is calculated as follow:

• pH   = pKIn - log [basic color] / [acidic color]

• pH   = pKIn +  log [basic color] / [acidic color]

• pH   = pKIn +  log [acidic color] / [basic color]

• pH   = pKw +  log [basic color] / [acidic color]

The "indigocarmine" indicator is an example of:

• universal indicator

• screened indicator

• turbidity indicator

• mixed indicator

which is true about the effective range of the indicator:

• should not exceed one pH unit

• pH = pKIn ± 1

• pH = pKIn

• the acid color = the basic color