Chemistry of Gases and Applications

Carbon dioxide is a colourless, odourless and linear molecule. Its structure can be represented as $O=C=O$ The $O-C-O$ bond angle is 180 $^o$. The carbon atom is $sp$ hybridised.

The chemicals used for testing oxygen are nitric oxide and alkaline pyragallol solution.

When $NO$ mixes with oxygen, reddish brown fumes of $NO _2$ appears.$2 NO _{(g)} + O _{2(g)}\rightarrow 2NO _{2(g)}$

The composition of biogas is :

Biogas is principally a mixture of methane (CH₄) and carbon dioxide (CO₂) along with hydrogen (H2) gas in small amount. It can be collected from landfills, covered lagoons, or enclosed tanks called anaerobic digesters. Biogas is commonly made from animal manure, sludge settled from wastewater, and at landfills containing organic wastes. Hence option C is correct.

Definition of biogas- The gas fermentation of animal during which takes place in the absence of air due to the presence of anaerobic bacteria. 

Biogas is primarily a mixture of methane and carbon dioxide, with smaller amounts of hydrogen, nitrogen, and hydrogen sulfide. Option A is the most accurate description among the choices.

     Easily liquefiable gases can adsorb more than the other gases.

As $CO _2$ is an easily liquefiable gas, hence it is adsorbed more by charcoal.

Activated charcoal adsorps poisonous gas thus used in the gas masks.

In the early 1990s, research confirmed that high concentrations of chlorine monoxide were a primary cause of ozone depletion over the poles.

Syngas is also called as water gas which is a mixture of carbon monoxide and hydrogen.

Burning hydrogen with oxygen give rise to formation of water.

Answer is B.

Biogas is characterized based on its chemical composition and the physical characteristics which result from it. It is primarily a mixture of methane (${ CH } _{ 4 }$) and inert carbonic gas (${ CO } _{ 2 }$). However the name 'biogas' gathers a large variety of gases resulting from specific treatment processes, starting from various organic waste - industries, animal or domestic origin waste, etc . 
Hence, the statement is false.

Fuel-grade ethanol is one energy source that has great potential for being generated from biomass. The gas obtained by the fermentation of biomass is called biogas.