Chemistry of Gases and Applications

Calorific value of LPG = 55,000 kJ/kg   Calorific value of biogas = 35000-40000 kJ/kg Calorific value of hydrogen = 1,50,000 kJ/kg

Carbon monoxide (CO) is highly poisonous because it binds to hemoglobin in red blood cells 200+ times more strongly than oxygen, preventing oxygen transport and causing asphyxiation. CO2 is not poisonous in normal concentrations but causes suffocation by displacing oxygen. Nitrogen is inert.

Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide and small amounts of other gases. Air also contains a variable amount of water vapour on average around 1%. In fact, air contains slightly less than 1% argon making it the third most abundant gas in air after nitrogen and oxygen. Argon is the most abundant and most used of the noble gases.

For combustion to occur (that is a fire to start), oxygen must be present. Fire is a chemical reaction that creates light and heat from oxygen and fuel. A lit candle needs to draw oxygen from the air in order to continue burning. If you limit the amount of air available, the candle's flame eventually goes out once it uses up all the oxygen. When a candle burns, the wax is reacting with oxygen in the air to give out heat and light. If you give the candle more oxygen, then it will burn brighter but it will burn out more quickly. It all depends whether the candle has a high or low concentration of oxygen.

When you breathe in, nitrogen gas will enter the blood and circulate around the body without being used up or added to. When it reaches the lungs, it will pass out again. The percentage of nitrogen inhaled is roughly 79% but it is only 74% when exhaled. Nitrogen is a rather inert gas that does not change density depending on temperature as readily as oxygen does. Nitrogen itself is not actually used up by the body. It is simply a byproduct of the nitrates and various emissions involved in photosynthesis from plants and various algae that get pumped with whimsical abandon into the atmosphere.

Methane is a compound and its elements are combined in fixed proportion.

Producer gas is CO + N₂. The core of lead pencil is made of non-toxic graphite and does not contain lead.

The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn).

Oxides of Sulphur cause breathing infection.

 Refrigerator, fire extinguisher and air conditioner emit CFCs in large quantities whereas DC motors do not emit CFCs.

Water vapor (H2O) constitutes about 60-90% of all volcanic gas emissions by volume. While CO2 and SO2 are significant, water vapor is by far the most abundant. Helium is present only in trace amounts. This makes option A correct.

Water is the most abundant compound on earth's surface, covering about 70 percent of the planet. In nature, water exists in liquid, solid and gaseous states.

Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u , hydrogen is the lightest element and its monatomic form (H1) is the most abundant chemical substance, constituting roughly 75% baryonic mass of the universe .

Water vapor (H2O in gaseous form) is by far the most abundant gas emitted during volcanic eruptions, typically accounting for 60-90% of total volcanic gas emissions. This occurs because hot magma contains dissolved water from the original molten rock and from interactions with groundwater. Carbon dioxide (CO2) is the second most abundant (10-40%), while sulfur dioxide (SO2) and other gases are emitted in much smaller quantities. Helium is rare.

Helium is mixed with oxygen for respiration by divers in deep sea.