Explore topic-wise InterviewSolutions in .

i. Mg is a metal.

ii. Br is a nonmetal.

iii. Antimony is a metalloid.

iv. Metalloids have properties of both metals and nonmetals.

v. Graphite is a good conductor of electricity.

Cations are formed by loss of electrons and anions are formed by gain of electrons.

Duralumin is light, strong and corrosion resistant.

3X - 6e^- → 3X²⁺

2Y + 6e^- → 2Y^3-

Y + 3e^– → Y3^– (cations formed).

(d) (Al₂O₃) + Na₃AlF₆ + CaF₂

X³⁺ formed is a cation and element ‘X’ has a valency of +3.

In the electrolysis of molten aluminium oxide, oxygen gas is liberated which gradually bums away carbon anode at a higher temperature to form carbon dioxide. 

C + O₂ ⟶ CO₂.

 If X³⁺ combines with oxygen the formula of the product is X₂O₃ .

 The ion X³⁺ loses electrons and gets reduced to neutral atoms.

If the above product in the molten state is electrolysed the ion X³⁺ will get discharged at the cathode. 

Functions of : 

(i) NaOH : Crushed and powdered bauxite is heated with a cone, solution of NaOH at 150-200°C for 2 hours under pressure. The main impurities present in bauxite (Fe₂O₃ and SiO₂) remain unaffected with cone. NaOH since these are not amphoteric. Bauxite, being amphoteric reacts with the base to form sodium aluminate, which is soluble in water. Thus NaOH helps in the purification of the ore. 

(ii) Cryolite : 

(a) To increase the mobility of the fused mixture. 

(b) To lower the fusion point of the mixture. 

(c) To increase the electrical conductivity of the mixture. 

(iii) Fluorspar : 

(a) To increase the mobility of the fused mixture

(b) To lower the fusion point of the mixture.

The liberated A₁ metal [m.p. 660°C] may also tend to volatize out and get wasted. Hence the fusion temperature of the electrolytic mixture has to be – lowered.

 The reasons for addition of mainly cryolite [in a higher ratio] and fluorspar to the electrolytic mixture are : 

(a) They lowers the fusion point of the mixture i. e. the mixture fuses [melts] around 950°C instead of 2050°C. 

(b) They enhances the mobility of the fused mixture by acting as a solvent for the electrolytic mixture. Thus cryolite in the molten state of subdivision dissolves aluminium oxide. 

(c) Addition of cryolite enhances the conductivity of the mixture. Since pure alumina is almost a non-conductor of electricity.

1. Wilfley table method 

2. Hydraulic separation method 

3. Magnetic separation method 

4. Froth floatation method 

5. Leaching method.

1. Wilfley table method

2. Hydraulic separation method are two methods of concentration of ores in which the heavy particles of ores can be separated from the light, gangue particles by the gravitational method.

Roasting:

1. In this process, the ore is heated strongly in the presence of air. 

2. In this process, sulphide ore is converted into metal oxide. 

3. During this process SO₂ is given out.

Calcination:

1. In this process, the ore is heated strongly in the limited supply of air. 

2. In this process, carbonate ore is converted into metal oxide. 

3. During this process CO₂ is given out.

Roasting : 

1. Ore is heated in the presence of air. 

2. Used generally for sulphide ores. SO₂ gas is given off. 2ZnS+ 3O₂ → 2ZnO + 2SO₂ 

3. Volatile impurities are removed as oxides. 

Calcination : 

1. Ore is heated in the absence of air. 

2. Hence Used generally for carbonate ores. Hence, CO₂ gas is given off. ZnCO₃ → ZnO + CO₂ . 

3. Moisture, organic impurities and volatile impurities are removed.

1. The rusting of iron can be prevented by painting, oiling, greasing or varnishing its surface. 

2. Galvanisation is another method of protecting iron from rusting by coating iron with a thin layer of zinc. 

3. Corrosion of iron is prevented by coating iron with noncorrosive substance like carbon. This process is termed as alloying.

(1) Corrosion of a metal can be prevented if the contact between metal and air is cut off. 

(2) Corrosion of a metal is prevented by coating with something which does not allow moisture and oxygen to react with it. 

(3) A layer of oil or paint or grease is applied on the surface of a metal to prevent corrosion. The rusting or corrosion of iron can be prevented by this method. 

(4) Corrosion is also prevented by coating a corrosive metal with a noncorrosive metal. Galvanising, tinning, electroplating, anodising and alloying are the different methods in which a metal is coated with a noncorrosive metal to prevent corrosion.

Corrosion is degradation of a material due toreaction with its environment.

i. True.

ii. True.

iii. False. 

(Ionic compounds are soluble in water and insoluble in kerosene.)

iv. False. 

(Ionic compounds in the solid state do not conduct electricity.)

v. False. 

(Mercury, silver and gold are least reactive metals.)