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

Options

A. `{:(,"Base","Acid","End point",),((a),"Weak","Strong","Colourless to pink",):}`
B. `{:(,"Base","Acid","End point",),((b) , "Strong","Strong","Pinkish red to yellow",):}`
C. `{:(,"Base","Acid","End point",),((b) , "Weak ","Strong","Yellow to pinkish red",):}`
D. `{:(,"Base","Acid","End point",),((b) , "Strong","Strong","Pink to colourless",):}`

Answer

C

Explanation

pH range of methyl orange is 3.1 - 4.5 . Below 3.1, it is pinkish red and above 4.5, it is yellow.
Weak base has `pH gt 7`. When methyl orange is added to weak base solution, the solution becomes yellow. When the solution is titrated with a strong acid, after the end point, solution is acidic and pH is `lt ` 3.1 . Therefore solution becomes pinkish red.