Explore topic-wise InterviewSolutions in .

1. HNO_2, HNO₃

2. The product of oxidation depends upon the concentration of the acid, temperature and the nature of the material undergoing oxidation, e.g.

(a). 3Cu + 8HNO₃ (dilute) → 3Cu(NO₃)₂ + 2NO + 4H₂O

Cu + 4HNO₃(conc.) → Cu(NO₃)₂ + 2NO₂ + 2H₂O

(b). Zinc reacts with dilute nitric acid to give N₂O and with concentrated acid to give NO₂. 

4Zn + 4HNO₃(dilute) → 4Zn(NO₃)₂ + 5H₂O + N₂O

Zn + 10HNO₃(conc.) → Zn(NO₃)₂ + 2H₂O + 2NO₂

Some metals (e.g., Cr, Al) do not dissolve in concentrated nitric acid due to the formation of a passive film of oxide on the surface.

a) i) N₂O

b) Laboratory preparation: In the laboratory, nitric acid is prepared by heating KNO₃ or NaNO₃ and concentrated H₂SO₄ in a glass retort.

NaNO₃ + H₂SO₄ → NaHSO₄ + HNO₃

Uses: in the manufacture of ammonium nitrate for fertilisers and other nitrates for use in explosives and pyrotechnics; for the preparation of nitroglycerin, trinitrotoluene and other organic nitro compounds; in the pickling of stainless steel etching of metals and oxidiser in rocket fuels.

OR

a) iii) PH₃

b) Preparation of PCI₃: By passing dry chlorine over heated shite phosphorus.

P₄ + 6Cl₂ → 4PCl₃

Or, by the action of thionyl chloride with white phosphorus.

P₄ + 8SOCl₂ → 4PCI₃ + 4SO₂ + 2S₂Cl₂

Properties of PCI₃: It is a colourless oily liquid and hydrolyses in the presence of moisture. Hence, it fumes in moist air.

PCI₃ + 3H₂O → H₃PO₃ + 3HCI

Structure of PCI₅: In gaseous and liquid phases, PCI₅ has a trigonal bipyramidal structure. The three equational P – CI bonds are equivalent, while the two axial bonds are longer than equatorial bonds. This is due to the fact that the axial bond pairs suffer more repulsion as compared to equatorial bond pairs.

XeF₆ on complete hydrolysis produces XeO₃

The molarity of given orthophosphoric acid solution is 2M. its normality is 6N

1. Nitrogen is used for the manufacture of ammonia, nitric acid and calcium cyanamide etc. 

2. Liquid nitrogen is used for producing low temperature required in cryosurgery, and so in biological preservation

Pure nitrogen gas can be obtained by the thermal decomposition of sodium azide about 575K

2NaN₃ + 575K ⟶ 2Na + 3N₂

Bond order for nitrogen molecule is 3

The group – 15 elements like nitrogen, phosphorous Arsenic, Antimony and Bismuth are collectively called as pnictogens. Their general outer electronic configuration is ns²np³

(a) Nitrogen

(b) Fractional distillation

Oxygen is not a pnictogens.

(c) A is correct but R is wrong

About 78% of earth atmosphere contains N.

(a) A and R are correct and R explains A

Ammonia reduces the metal oxides to metal when passed over heated metallic oxide.

3PbO + 2NH₃ → 3Pb + N₂ + 3H₂O

(d) 1s² 2s² 2p⁶ 3s² 3p³

Nitric acid reacts with bases and basic oxides to form salts and water.

1. ZnO + 2HNO₃ → Zn(NO₃)₂ + H₂O 

2. 3FeO + 10HNO₃ → 3Fe(NO₃)₃ + NO + 5H₂O

1. Magnesium with cone. HNO₃ : 

4Mg + 10HNO₃ → 4Mg(NO₃)₂ + NH₄NO₃ + 3H₂O Magnesium reacts with concentraated nitric acid to gives both magnesium nitrate and ammonium nitrate.

2. Magnesium with dil HNO₃ :

Magnesium reacts with dilute nitric acid to gives both magnesium nitrate and nitrous oxide. 

4Mg + 10HNO₃ → 4 Mg(NO₃)₂ + N₂O + 5H₂ O

(i) d 

(ii) a 

(iii) b 

(iv) c

(b)  Sulphur

Nitric acid is prepared by heating equal amounts of potassium or sodium nitrate with concentrated sulphuric acid.

KNO₃ + H₂SO₄ → KHSO₄ + HNO₃ 

The temperature is kept as low as possible to avoid decomposition of nitric acid. The acid condenses to a fuming liquids which is coloured brown by the presence of a little nitrogen dioxide which is formed due to the decomposition of nitric acid. 

4HNO₃ → 4NO₂ + 2H₂O + O₂

1. Nitric acid is used as a oxidising agent and in the preparation of aquaregia. 

2.  Salts of nitric acid are used in photography (AgNO₃) and gunpowder for firearms. (NaNO₃) .

When sodium nitrite reacts with ferrous sulphate in the presence of sulphuric acid to gives nitric oxide. 

2NaNO₂ + 2FeSO₄ + 3H₂S → Fe₂(SO₄)₃ + 2NaHSO₄ + 2H₂O + 2NO

(a) HOCl = +2

(i) b 

(ii) c 

(iii) d 

(iv) a

Cl₂ is used for purification of drinking water.

Nitric acid prepared in large scales using Ostwald’s process. In this method ammonia from Haber’s process is mixed about 10 times of air. This mixture is preheated and passed into the catalyst chamber where they come in contact with platinum gauze. The temperature rises to about 1275 K and the metallic gauze brings about the rapid catalytic oxidation of ammonia resulting in the formation of NO, which then oxidised to nitrogen dioxide.

4NH₃ + 5O₂ → 4NO + 6H₃O + 120kJ

2NO + O₂ → 2NO₃

The nitrogen dioxide produced is passed through a series of adsorption towers. It reacts with water to give nitric acid. Nitric acid formed is bleached by blowing air.

6NO₂ + 3H₂O → 4HNO₃ + 2NO + H₂O

(c) N₂O₃ = +5

(b) Nitroso ferrous sulphate

(i) c 

(ii) d 

(iii) a 

(iv) b

(i) b 

(ii) a

(iii) d 

(iv) c

(i) d 

(ii) c 

(iii) a 

(iv) b

Nitrogen sesquoxide colour is Blue

Quartz is three dimensional silicates.

Silicates: The mineral which contains silicon and oxygen in tetrahedral [SiO₄]^4- units linked together in different patterns are called silicates. 

Types of Silicates:

1. Ortho silicates 

2. Pyro silicates 

3. Cyclic silicates 

4. Ino silicates 

5. Phyllo silicates 

6. Tecto silicates

1. All silicones are water repellent. 

2. They are thermal and electrical insulators. 

3. Chemically they are inert. 

4. Lower silicones are oily liquids whereas higher silicones with long chain structure are waxy solids. 

5. The viscosity of silicon oil remains constant and doesn’t change with temperature and they don’t thicken during winter.

All silicones are water repellent, this is due to the presence of organic side groups that surrounds the silicon which makes the molecule looks like an alkane. Therefore silicones are water repellent.

(i) P₄ + 3NaOH + 3H₂O → PH₃ + 3NaH₂PO₂

(ii) PCl₅ \(\overset{Heat}{\rightarrow}\) PCl₃ + PCl₂

(iii) I₂ + 10HNO₂ (conc. ) → 2HIO₃ + 10NO₂ + 4H₂O

The electrode potential of F₂ (+ 2.87V) is much higher than that of Cl₂ (+ 1.36V) therefore, F₂ is a much stronger oxidising agent than Cl₂.

This can be explained as under:

Electrode potential depends upon three factors:

1. bond dissociation enthalpy

2. electron gain enthalpy

3. hydration enthaply.

Although electron gain enthalpy of fluorine is less negative (-333 kJ mol^-1) than that of chlorine (-349 kJ mol^-1) the bond dissociation enthalpy of F – F bond is much lower (158.8 kJ mol^-1) than that of Cl – Cl bond (246.6 kJ mol^-1) and hydration enthalpy of F^– ion (515kJ mol^-1) is much higher than that of Cl^–ion (381 kJ mol^-1).

The last two factors are more that compensate the less negative electron gain enthalpy of F₂. As a result, electrode potential of F₂ is higher than that of Cl₂ and hence F₂ is a much stronger oxidising agent than Cl₂.

(i) C₂H₄ undergoes combustion to form CO₂ and H₂O.

C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

(ii) Al combines with 0, to form alumina.

4Al + 3O₂ → 2Al₂O₃

Three areas in which H₂SO₄ plays an important role are given below:

1. It is used as electrolyte in storage batteries.

2. It is used in petrolium refining, detergent industry and in the manufacture of paints, pigments, dyes etc.

3. H₂SO₄ is used in the manufacture of fertilizers such as ammonium sulphate, calcium super-phosphate.

(d) Al, Cu, Mn, Mg

Al – 95% , Cu – 4% , Mn – 0.5% , Mg – 1.1 %

(i) Carbon is the most non-metallic element of group 14 and hence its dioxide is most acidic. 

(ii) Lead is most stable in +2 oxidation state due to inert pair effect. 

(iii) Silicon and germanium are used as semiconductors.

(i) Ni + 4CO \(\underset{80^oC}{\stackrel{Heat}{\rightarrow}}\) Ni(CO)₄

(ii) Ni + 4CO → CaC₂ + CO

(iii) CO + Cl₂ → COCl₂

Silicate contains [SiO₂]^4- silicon and oxygen in units.

When potash alum is heated at 365 K. It melts and form molten state. Again heated at 475 K they lose water of hydration and swells up. Thee swollen mass is known as burnt alum.

(a) Oxo process

1. Silicon tetrachloride is used in the production of semiconducting silicon.

2. It is used as a starting material in the synthesis of silica gel, silicic esters, a binder for ceramic materials

Essential condition for catenation: 

1. The valency of elements is greater than or equal to two. 

2. Element should have an ability to bond with itself. 

3. The self bond must be as strong as its bond with other elements. 

4. Kinetic inertness of catenated compound towards other molecules.

(b) hexagonal