A laboratory mixture contains iron filings, saw-dust, and common salt. Which sequence of physical separation…

A laboratory mixture contains iron filings, saw-dust, and common salt. Which sequence of physical separation methods will cleanly isolate all three substances?
  1. Dissolve mixture in water $\rightarrow$ Magnetic separation $\rightarrow$ Evaporation
  2. Magnetic separation $\rightarrow$ Add water to remaining mix and filter $\rightarrow$ Evaporate filtrate
  3. Winnowing $\rightarrow$ Sieving $\rightarrow$ Magnetic separation
  4. Centrifugation $\rightarrow$ Distillation $\rightarrow$ Decantation

Solution

A magnet first removes iron filings. Adding water dissolves the salt while saw-dust remains insoluble. Filtration collects saw-dust on the filter paper, and evaporating the liquid filtrate leaves pure salt.

Asked in: Homi Bhabha Practice

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