Question

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

• A. Strong base- strong acid- pink to colourless
• B. Weak base-strong acid- colourless to pink
• C. Strong base- strong base- pinkish red to yellow
• D. Weak base- strong acid- yellow to pinkish red

Answer 1

The correct option is D Weak base- strong acid- yellow to pinkish red

Methy orange is a weak organic base. It is used in the titration of weak base vs strong acid
$MeOH\rightleftharpoons M{e}^{+}+O{H}^{-}$
yellow red
In alkaline medium, the equilibrium lies in the backward direction and therefore it shows yellow colour. In acidic medium, the equilibrium shifts to the forward direction and therefore, the colour changes from yellow to red.