Question

An alkali is titrated against an acid with methyl orange as indicator, which of the following is a correct combination?

• A. Base- Strong , Acid- Strong , End point - Pink to colourless
• B. Base - Weak , Acid- Strong , End point - Colourless to pink
• C. Base - Strong , Acid- Strong , End point - Pinkish red to yellow
• D. Base - Weak , Acid- Strong , End point - Yellow to pinkish red

Answer 1

Answer: (D)

Methyl orange is weak organic base. It is used in the titration of weak base vs strong acid.

In basic medium, equilibrium lies in backward direction, and therefore it shows yellow colour.
In acidic medium, equilibrium shifts in forward direction and therefore, colour changes from yellow to red.