Consider the following statements about the commercial alcohols methanol and ethanol.
(A) Methanol is produced by catalytic hydrogenation of carbon monoxide over ZnO–Cr2O3 catalyst at 200–300 atm and 573–673 K.
(B) Ethanol is used as a solvent in the paint industry and in the preparation of a number of carbon compounds.
(C) Nowadays, large quantities of ethanol are obtained by hydration of ethyne.
(D) Commercial alcohol is made unfit for drinking by mixing in it some copper sulphate, which gives it a foul smell.
Which of the statements given above are incorrect? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (C) and (D) only
Methanol and ethanol are the two commercially important alcohols. Methanol is now made from carbon monoxide and hydrogen; ethanol is made by fermentation of sugars and, in large quantities, from ethene.
(A) Methanol is produced by catalytic hydrogenation of carbon monoxide over ZnO–Cr2O3 catalyst at 200–300 atm and 573–673 K. — Correct statement. Carbon monoxide adds two molecules of hydrogen at high pressure and temperature:
\( \displaystyle \ce{CO + 2H2} \xrightarrow[\text{200-300 atm, 573-673 K}]{\ce{ZnO-Cr2O3}} \ce{CH3OH} \)
(B) Ethanol is used as a solvent in the paint industry and in the preparation of a number of carbon compounds. — Correct statement. These are the uses of ethanol, a colourless liquid boiling at 351 K.
(C) Nowadays, large quantities of ethanol are obtained by hydration of ethyne. — Incorrect statement. Ethanol is obtained by hydration of ethene, the alkene CH2=CH2; acid-catalysed addition of water to it gives ethanol: \( \ce{CH2=CH2 + H2O} \xrightarrow{\ce{H+}} \ce{CH3CH2OH} \).
(D) Commercial alcohol is made unfit for drinking by mixing in it some copper sulphate, which gives it a foul smell. — Incorrect statement. In denaturation, copper sulphate is added to give the alcohol a colour; the foul smell comes from pyridine, which is added along with it.
NCERT (2026-27 edition):
7.5 Some Commercially Important Alcohols – “Methanol, CH3OH, also known as ‘wood spirit’, was produced by destructive distillation of wood. Today, most of the methanol is produced by catalytic hydrogenation of carbon monoxide at high pressure and temperature and in the presence of ZnO – Cr2O3 catalyst.”
\( \displaystyle \ce{CO + 2H2} \xrightarrow[\text{200-300 atm, 573-673 K}]{\ce{ZnO-Cr2O3}} \ce{CH3OH} \)
“Ethanol is a colourless liquid with boiling point 351 K. It is used as a solvent in paint industry and in the preparation of a number of carbon compounds. The commercial alcohol is made unfit for drinking by mixing in it some copper sulphate (to give it a colour) and pyridine (a foul smelling liquid). It is known as denaturation of alcohol. Nowadays, large quantities of ethanol are obtained by hydration of ethene (Section 7.4).”