In the titration of I 2(a q) by S 2 O 32-(a q) using the starch indicator, the end point is indicated by

Question

In the titration of I 2(a q) by S 2 O 32-(a q) using the starch indicator, the end point is indicated by (A) colourless to blue (B) blue to colourless (C) pink to colourless (D) blue to pink

Tardigrade Admin · Accepted Answer

The chemical reaction involved during the titration of

I_{2} (a q)

by

S_{2} O_{3}^{2 -} (a q)

using starch indicator is

I_{3}^{-} + 2 S_{2} O_{3}^{2 -} ⟶ S_{4} O_{6}^{2 -} + 3 I^{-}

At the end point deep blue colour disappears due to the decomposition of the iodine-starch complex. Thus, the colour change at end point is from blue to colourless.

Q. In the titration of I2​(aq) by S2​O32−​(aq) using the starch indicator, the end point is indicated by

colourless to blue

blue to colourless

pink to colourless

blue to pink

Q. In the titration of $I_{2} (a q)$ by $S_{2} O_{3}^{2 -} (a q)$ using the starch indicator, the end point is indicated by