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JEE Main202324 Jan 2023Evening ShiftChemistryd and f Block ElementsActual

K 2 Cr 2 O 7 paper acidified with dilute H 2 SO 4 turns green when exposed to

Options

  1. ACarbon dioxide
  2. BSulphur trioxide
  3. CHydrogen sulphide
  4. DSulphur dioxide

Correct answer

D. Sulphur dioxide

Step-by-step solution

Carbon dioxide and sulphur trioxide cannot undergo oxidation. Potassium dichromate is reduced to chromic sulphate in the presence of sulphur dioxide. The orange solution of potassium dichromate becomes green colour chromic sulphate. K 2 Cr 2 O 7   +   3 SO 2   +   H 2 SO 4   →   K 2 SO 4   +   Cr 2 ( SO 4 ) 3   +   H 2 O Hence, the gas is sulphur dioxide.

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