Sample 1Medium
In a combustion apparatus, 0.246 g of an organic compound is heated with copper(II) oxide; the gases pass first through a U-tube of anhydrous calcium chloride and then through a U-tube of potassium hydroxide solution. The CaCl2 tube gains 0.1014 g and the KOH tube gains 0.198 g. What is the percentage of carbon in the compound?
Show the answer
The answer is B.
The KOH tube absorbs CO2, of which 12/44 is carbon. % C = (12 × 0.198 × 100)/(44 × 0.246) = 21.95%.
- A.
This uses the mass gained by the CaCl2 tube, which absorbs water, not carbon dioxide.
- C.
4.58% is the percentage of hydrogen, calculated from the water absorbed by CaCl2.
- D.
This takes the whole mass of CO2 as carbon; only 12/44 of it is carbon.
NCERT: Class 11 Chemistry, Chapter 8