Page 216 - Chemistry ICSE Class IX
P. 216
1 Recognition and
Identification of Gases
BASIC CONCEPTS
Gases can be recognised and identi ed from some of their characteristic properties, such as
y Colour Gases like Oxygen (O ),
2
Nitrogen (N ), Hydrogen (H ),
2
2
y Odour Chlorine (Cl ), etc. are called
2
elementary gases.
y Chemical behaviour, such as action on litmus and burning
characteristics. Gases like Carbon dioxide
(CO ), Hydrogen sulphide
2
On the basis of chemical behaviour, gases can be classi ed into the following (H S), Nitrogen dioxide (NO ),
2
2
three categories: etc. are called compound
gases.
y Acidic gases: Carbon dioxide (CO ), Sulphur dioxide (SO ), Chlorine
2 2
(Cl ), Hydrogen chloride (HCl), Hydrogen sulphide (H S), Nitrogen dioxide (NO )
2
2
2
y Neutral gases: Oxygen (O ), Hydrogen (H ), Water vapour [H O(g)], Nitrous oxide (NO)
2
2
2
y Basic gas: Ammonia (NH )
3
EXPERIMENT 1.1
Objective
To identify some common gases
Gas and its Source Observations Inference
1. HYDROGEN
Hydrogen gas is evolved when dilute Colourless Cl and NO are absent.
2
2
hydrochloric acid or dilute sulphuric Odourless Gas may be O , H , Water vapour
2
acid is added to any reactive metal, [H O(v)] or CO . 2
such as Zn and Mg. 2 2
No effect on litmus The gas is neutral.
Burns with a RCNG DNWG ƀCOG In ammable gas, burns
producing popping sound. explosively in air.
The gas evolved is hydrogen.
2. OXYGEN
Evolves on heating either of the Colourless Cl and NO are absent.
2
2
following: Odourless Gas may be O , H , H O(v) or CO .
2
2
2
2
Metal nitrates, KNO 3 No effect on litmus Gas is neutral.
Oxides: PbO , Pb O , HgO The smouldering splinter bursts Gas is a supporter of combustion.
2 3 4
Potassium chlorate, KClO 3 into ame The gas evolved is oxygen.
