Page 218 - Chemistry ICSE Class IX
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206 ICSE Chemistry – 9
Gas and its Source Observations Inference
8. HYDROGEN CHLORIDE
Evolves when conc. H SO is reacted Colourless gas Cl and NO are absent.
2 4 2 2
with a metal chloride or ammonium Irritating odour Gas may be SO or HCl.
2
chloride Turns moist blue litmus red Gas is an acidic gas – may be SO 2
Dense white fumes produced or HCl.
when rod dipped in NH OH Gas formed dense white fumes of
4
solution is brought near to it ammonium chloride.
The gas evolved is hydrogen
chloride.
9. NITROGEN DIOXIDE
Evolves by the Brown coloured gas Cl is absent.
2
action of conc. H SO on metal Irritating odour Gas may be NO .
2
4
2
nitrates Turns moist blue litmus red Gas is an acidic gas.
decomposition of certain metal Turns potassium iodide (KI) Gas is an oxidising agent.
nitrates on heating paper brown The gas evolved is NO .
2
10. CHLORINE
Evolves by the Greenish-yellow gas Gas is chlorine (Cl ).
2
action of conc. HCl on manganese Choking odour Gas is chlorine (Cl ).
2
dioxide It turns moist blue litmus to It is an oxidising agent.
action of dilute acids on bleaching red and nally bleaches it i.e.,
powder decolourises it
Turns starch-iodide paper blue or It is stronger oxidising agent than
blue-black iodine. It may be Cl .
2
The gas evolved is chlorine.
VIVA VOCE
1. Name two colourless and odourless gases.
Ans. Hydrogen, Oxygen.
2. Name a colourless and odourless gas that turns limewater milky.
Ans. Carbon dioxide gas turns limewater milky.
3. Identify a colourless gas having irritating odour and
(a) turning moist red litmus blue.
(b) giving dense white fumes when a rod dipped in conc. hydrochloric acid is brought closer to it.
(c) Write the chemical equation for the reaction that takes place in (b).
Ans. The gas is ammonia.
Ammonia gives dense white fumes due to the formation of ammonium chloride.
NH (g) + HCl(vap) o NH CI(s)
3 4
moist fine particles of
ammonium chloride
4. A gas smells like rotten eggs and turns lead acetate paper silvery black. Identify the gas. Write the chemical equation for
the reaction.
Ans. The gas that smells like rotten eggs is hydrogen sulphide (H S).
2
