Question

Which of the following colour changes shown during redox titrations is not correct?

• A. $Cr_{2}O_{7}^{2 -}$oxidises the indicator diphenylamine to produce blue colour showing end point.
• B. Iodine formed by oxidation of $I^{-}$ ions gives blue colour with starch showing end point.
• C. $KMnO_{4}$in the form of $MnO_{4}^{-}$ions gives pink colour showing end point.
• D. Thisulphate ions $(S_{2}O_{3}^{2 -})$ give blue colour showing end point.

Answer 1

Answer: (D)

Thisulphate ions $(S_{2}O_{3}^{2 -})$ give blue colour showing end point.

Answer 2

: Thiosulphate ions do not act as indicator and do not indicate end point by change in colour.