Define indicator. Why are different indicators used in different pH ranges ?

Why oils of different viscosity are used in different seasons?

The pH indicators are

Define the term Activation energy. Why different reactions proceed at different speeds ?

Different Types Of Indicator

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