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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2024 · Paper I

Q4(a). Lead–silver eutectic and desilverisation

Question

Draw the phase diagram of lead–silver system. Explain its significance in desilverization of lead.

Answer in brief

The simple eutectic diagram explains Pattinson desilverisation: cooling a Pb-rich melt crystallises nearly pure Pb and enriches silver in the residual liquid until the eutectic is reached.

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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.

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Topic notes: the phase rule, phase diagrams, the Clausius–Clapeyron equation, eutectics and partially miscible liquids, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverslead-silver systemeutectic phase diagramPattinson processdesilverisation of leadreduced phase rule

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