Study of Compounds ICSE CHEMISTRY CLASS 10 - Reasoning Based Questions

ICSE CHEMISTRY CLASS 10 Study of Compounds - ALL GIVE REASONS

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.