Different gases have different physical and chemical properties. We can identify gases using those properties. Some gases have colours and smells as physical properties. As chemical properties, some gases are combustible, dissolve in water and react with water, behave as an acid or base, react with metals or non metals. Gases are released when some solid compounds are heated.
In this tutorial we discuss about what are the gases in the world, properties of gases, how these gases are prepared, reactions of them, identifying gas.
Following gases are formed frequently in laboratory reactions.
We study specific characteristics of some gases.
Acidic gases dissolve in water and react with water to give H3O+ ions.
CO2 dissolves in water and give carbonic acid(H2CO3). H2CO3 is a weak acid and a dibasic acid.
Second dissociation is more weaker than first dissociation.
Ammonia behave as a basic gas. NH3 gas dissolve very well in water and give ammonium hydroxide (NH4OH). NH4OH is a weak base.
Some gases readily react with oxygen. Therefore identifying those gases is secure to prevent accidents.
Nitrogen dioxide(NO2) and sulfur dioxide(SO2) gases are the main gases to cause acid rains. Acid rain can contain nitric acid (HNO3.) or and sulfuric acid(H2SO4) or both.
NO2 reacts with water and forms HNO3 acid which comes down as the acid rain.
SO2 reacts with O2 in the air under the influence of sunlight producing SO3 which can react with rain water to produce H2SO4 acid contributing to acid rain.
Nitrogen dioxide(NO2), unburnt hydrocarbons contain in the exhaust gases of vehicle engines. These vehicle exhaust cause to form harmful substances such as ozone(O3), aldehydes and peroxyacyl nitrates(PAN). NO2 dissociates as a result of the UV radiation from the sunlight forming free radicals resulting number of chain reactions.