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JEE Main 202324 JanuaryEvening Shift
Exam
JEE Main
Year
2023
Date
24 January
Shift
Evening Shift
Subject
Chemistry
Chapter
d and f Block Elements

JEE Main 2023 · 24 January · Evening Shift · Chemistry · d and f Block Elements

K _ 2 Cr _ 2 O _ 7 paper acidified with dilute H _ 2 SO _ 4 turns...

K2Cr2O7{K}_{2}{Cr}_{2}{O}_{7} paper acidified with dilute H2SO4{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.

K2Cr2O7+3SO2+H2SO4→K2SO4+Cr2(SO4)3+H2O{K}_{2}{Cr}_{2}{O}_{7} + 3{SO}_{2} + {H}_{2}{SO}_{4} \to {K}_{2}{SO}_{4} + {Cr}_{2} ( {SO}_{4}{)}_{3} + {H}_{2}O

Hence, the gas is sulphur dioxide.

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