Q7(b). Iodine titrations and starch
Answer the following: (i) What is the difference between iodimetry and iodometry? (ii) Why is iodine used in a solution containing excess I⁻? (iii) Why is starch used as an indicator in titrations involving iodine? (iv) Is starch a redox indicator? (v) In iodometric titrations, the contents of the reaction mixture are usually kept in dark after adding KI solution. Why?
Answer in brief
Iodimetry uses iodine directly; iodometry measures iodine liberated by an oxidant. Excess I⁻ solubilises I₂ as I₃⁻. Starch is a sensitive specific indicator, not a redox indicator.
Part of VKC Basic
Read the key points and the full model answer with VKC Basic
VKC Basic (₹999 for 6 months) opens every solved answer, the notes, the handbook and the daily answer archive. Every Mains test series includes it.
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
Coversiodometryiodimetrystarch indicatortriiodide I3-sodium thiosulfate titration
All parts of Question 7
- 7(a) Permanganate potential at pH 310 marks
- 7(b) Iodine titrations and starch10 marks
- 7(c) Will silver nitrate dissolve all the copper?10 marks