11. Which one of the following is water gas ?

Which one of the following is water gas ?

Mixture of carbon monoxide and hydrogen
Mixture of carbon monoxide and nitrogen
Mixture of carbon dioxide and water vapour
Mixture of carbon monoxide and water vapour
This question was previously asked in
UPSC NDA-1 – 2016
The correct option is A.
Water gas is a synthesis gas mixture primarily consisting of carbon monoxide (CO) and hydrogen (H₂). It is produced by passing steam over hot carbon (like coke or coal) at high temperatures (typically 700-1000 °C). The reaction is C + H₂O → CO + H₂.
Producer gas is another type of synthesis gas, produced by passing air over hot carbon, and primarily consists of carbon monoxide (CO) and nitrogen (N₂), along with some hydrogen and carbon dioxide. Water gas is a more energy-rich fuel than producer gas because it contains hydrogen and lacks the large proportion of inert nitrogen.

12. What are the main constituents of biogas?

What are the main constituents of biogas?

Methane and sulphur dioxide
Methane and carbon dioxide
Methane, hydrogen and nitric oxide
Methane and nitric oxide
This question was previously asked in
UPSC CDS-2 – 2017
The correct option is B) Methane and carbon dioxide.
Biogas is produced through the anaerobic digestion of organic matter by microorganisms. Its primary constituents are methane (CH₄), typically making up 50-75% of the volume, and carbon dioxide (CO₂), making up 25-50%. Methane is the main combustible component that gives biogas its value as a fuel.
Other gases present in biogas in smaller quantities may include hydrogen sulfide (H₂S), nitrogen (N₂), and hydrogen (H₂). Sulphur dioxide and nitric oxide are not typical main constituents of biogas; they are more associated with combustion processes or air pollution.