UPSC Combined Geo-Scientist, Mains · 2019 · Mains Paper III

Q2(d). Errors in iodine titrations with starch

5 marks
Topic: Analysis of geological materials
Question only

Question

Numerous analytical procedures are based on titrations involving iodine, with starch as the indicator. What can be the sources of error in these procedures and how can they be avoided?

Model answer

The free solution for 2019 answers questions 1, 3, 4, 6, 7 and 10, the ones picked in its time plan. This part is not answered on the site yet. New answers are announced on Telegram.

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Coversiodometry errorsstarch indicatoriodine volatilityair oxidation of iodide

All parts of Question 2

2(a) Degree of hydrolysis and pH of 0.01 M Na₂CO₃10 marks
2(b) Bringing a sparingly soluble salt into solution10 marks
2(c) Why Eriochrome Black T fails for Cu²⁺, Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺, Al³⁺5 marks
2(d) Errors in iodine titrations with starch5 marks