Acid-Base Indicators

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There are three acid-base indicators. Methyl orange (end point at pH=4 ), bromothymol blue (end point at pH-7 ), phenolphthalein (end point at pH=9 ). Which is the most suitable indicator for the following titrations? (a). H_2SO_4 with KOH (b). KCn with HCl (c). NH_3 with HNO_3 (d). HF with NaOH

Acid-base indicator such as methy 1 orange, phenolphthalein, and bromothymol blue ate substances which change colour accroding to the hydrogen ion concentration of the solution to which they are added. Most indicators are weak acids (or more rarely weak base) in which the undissociated and dissociated forms have different and distinct colours. If methy 1 orange is used as the examples and the un-dissociated forms is written as HMO , then dissociation occurs as shown below: Reaction: {:(HMOhArr,H^(o+)+,MO^(Theta),,),(Red,"Colourless","Yellow",,):} The indicator should have a sharp colour change with the equivalence point of the titration. Usually the colour change of the indicator occurs over a range of about two pH units. It should be noted that the eye cannot detect the exact end point of the tiytration. The pK_(a) of the indicator should be near the pH of the solution at the equivalance point. Given that the K_(a) (methy 1 orange) = 4.0 xx 10^(-4) , a solution at pH = 2 containing the indicator would be

Acid-base indicator such as methy 1 orange, phenolphthalein, and bromothymol blue ate substances which change colour accroding to the hydrogen ion concentration of the solution to which they are added. Most indicators are weak acids (or more rarely weak base) in which the undissociated and dissociated forms have different and distinct colours. If methy 1 orange is used as the examples and the un-dissociated forms is written as HMO , then dissociation occurs as shown below: Reaction: {:(HMOhArr,H^(o+)+,MO^(Theta),,),(Red,"Colourless","Yellow",,):} The indicator should have a sharp colour change with the equivalence point of the titration. Usually the colour change of the indicator occurs over a range of about two pH units. It should be noted that the eye cannot detect the exact end point of the tiytration. The pK_(a) of the indicator should be near the pH of the solution at the equivalance point. Which of the following sitution exists at the equivalence point of titration?

Which of the following is an acid -base indicator ?

Name the acid-base indicator extracted from lichens.

During the titration of a weak base with a strong acid, one should use an acid-base indicator that changes colour in the :