ICSE CHEMISTRY CLASS 10 Study of Compounds - ALL GIVE REASONS
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Give Reason
1.
HCl gas is not collected over water.
Ans:
HCl is highly soluble in water.
2.
In the laboratory preparation of HCl, temperature is maintained below 2000C.
Ans:
- To save fuel. If temperature is above 2000C, a hard crust of
Sodium sulphate is formed in the round bottom flask.
3.
HCl gas exposed to Ammonia gives white dense fumes.
Ans:
HCl combines with Ammonia to form Ammonium
chloride fumes.
4.
Conc. HNO3 is not used instead of Conc. Sulphuric acid in the
preparation of HCl gas.
Ans:
Conc HNO3 being a volatile acid, it cannot displace another volatile
acid i.e. HCl from NaCl.
5.
Hydrochloric acid is not prepared by dissolving HCl gas directly in water.
Ans:
Direct dissolution of HCl in water causes back-suction which may cause breakage
to the apparatus.
6.
HCl gas cannot be dried using quick lime.
Ans:
HCl reacts with basic Calcium oxide (Quick lime) and gives Calcium chloride.
7.
HCl in water conducts electricity but in Toluene does not.
Ans:
HCl gets ionized in water but in Toluene
does not.
8.
HCl gas fumes in moist air but H2S does not.
Ans:
HCl is highly soluble in water hence it forms mist with atmospheric moisture,
where as H2S is slightly soluble in water.
1.
In the laboratory preparation of Ammonia, Calcium hydroxide is taken in excess
quantity.
Ans: To prevent sublimation of Ammonium chloride.
2.
Ammonium nitrate is not used in the preparation of Ammonia gas.
Ans: Ammonium nitrate on heating decomposition to give Nitrous
oxide.
(or) Ammonium nitrate is explosive.
3.
Conc. H2SO4 is not used as a drying agent for
Ammonia gas.
Ans: Conc. H2SO4 reacts with ammonia to give
Ammonium sulphate.
4.
Round bottom flask is kept in inclined position in the preparation of Ammonia
in laboratory preparation of Ammonia.
Ans: To avoid water from trickling down the
round bottom flask which may cause cracks.
5.
NaOH is not preferred in the laboratory preparation of Ammonia gas.
Ans: Sodium hydroxide is a deliquescent substance.
6.
Metal nitrides are not preferred to prepare Ammonia gas.
Ans: Metal nitrides are expensive.
7.
In Haber’s process the reaction mixture is heated initially only.
Ans: It is an exothermic reaction.
8.
Lead hydroxide is insoluble in excess Ammonium hydroxide but Copper hydroxide
is soluble.
Ans: Copper hydroxide with excess Ammonium hydroxide forms a water
soluble complex compound but Lead hydroxide does not.
9.
Ammonia gas is not collected over water.
Ans: Ammonia is highly soluble in water.
10.
Platinum continues to glow even after the heating is discontinued in catalytic
oxidation of Ammonia gas.
Ans: The reaction is an exothermic reaction.
11.
Liquid Ammonia is used as a refrigerant.
Ans:
Liquid Ammonia evaporates by absorbing the heat quickly.
12.
Ammonium hydroxide is weak base.
Ans:
Ammonium hydroxide solution contains a
less concentration of Hydroxide ions.
1.
Pure Nitric acid takes yellow brown colour when exposed to the light.
Ans:
Nitric acid decomposes to give Nitrogen dioxide which remains dissolved in
Nitric acid which imparts the yellow colour to the acid.
2.
Only all glass apparatus should be used in the laboratory preparation of Nitric
acid.
Ans:
Highly corrosive Nitric acid vapours attack the rubber or cork but not glass.
3.
Iron is rendered passive with fuming Nitric acid.
Ans:
Nitric acid oxidizes Iron which results in the formation of a layer which stops
the further reaction.
4.
Nitric acid prepared in lab is in yellow colour.
Ans:
Nitrogen dioxide remains dissolved in Nitric acid.
5.
Dil. Nitric acid does not give Hydrogen gas with active metals.
Ans:
Dilute nitric acid being an oxidizing agent oxidizes Hydrogen to Water.
6.
Higher ratio of air is used in Ostwald’s process.
Ans:
Oxygen is required in the all the three steps of the process.
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