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JEE Advanced levelSingle correct optionDifficulty 3 of 3si194

In a Liebig combustion train the tube of anhydrous (absorbs water) is normally placed before the tube of concentrated KOH solution (absorbs , and also absorbs water vapour). If by mistake the KOH tube is placed first, the calculated results will show

  1. Apercentage of C too low and percentage of H too high
  2. Bboth percentages too high
  3. Cno error, because both tubes absorb independently
  4. Dpercentage of C too high and percentage of H too low

Answer: D

The KOH solution absorbs both and the water vapour. Its mass gain is therefore larger than the alone (so %C is too high), while the tube now receives little or no water (so %H is too low).
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