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1. Sulphuric acid is used in the manufacture of fertilisers, ammonium sulphate and super phosphates and other chemicals such as hydrochloric acid, nitric acid etc… 

2. It is used as a drying agent and also used in the preparation of pigments, explosives etc..

ICl bond is weaker than I – I bond. Therefore ICl can break easily to form halogen atoms which readily brings about the reaction.

(a) A and R are correct but doesn’t explains A

Due to the presence of triple bond between the two nitrogen atoms, the bond dissociation energy of N₂ (941.4 kJ mol^-) is very high. Therefore, N₂ is less reactive at room temperature.

Fluorine is the most reactive element among halogen. This is due to the minimum value of F – F bond dissociation energy. Hence fluorine is more reactive than other halogens.

(d) HCIO < HClO₂ < HClO₃ < HCIO₄

The hydrogen halides are extremely soluble in water due to the ionisation. 

X + H₂O → H₃O⁺ + X^-

(X = F, Cl, Br or I)

Solutions of hydrogen halides are therefore acidic and known as hydrohalic acids. Hydrochloric, hydrobromic and hydroiodic acids are almost completely ionised and are therefore strong acids but HF is a weak acid. For HF,

• HF + H₂O ⇌ H₃O⁺ + F^- 
• HF + F^- → HF₂^-

At high concentration, the equilibrium involves the removal of fluoride ions is important. Since it affects the dissociation of hydrogen fluoride, therefore it is a weak acid.

(a)  Fluorine

(c)  (i) and (iii)

(d) HI > HBr > HCI > HF

(d) Helium – flash bulbs

Square planar

(i) It is because NO₂ contains odd number of valence electrons. On dimerisation, it is converted to stable N₂O₄ , molecule with even number of electrons.

(ii) In group-15 the stability of +5 oxidation state decreases and that of +3 oxidation state increases due to inert pair effect.

Thus, BiCl₃ , is more stable than BiCl₅.

Helium is used in diving apparatus because of its very low solubility in blood.

Due to high charge and small size of sulphur in +6 oxidation state in SO₃ it is more covalent than SO₂, in which sulphur is in +4 oxidation state.

Halon – 1301 is C₂ F₄ Br₂ .

3. A is true, but R is false. 

3. A is true, but R is false.

Diamond has three-dimensional network structure involving strong C-C bonds. These bonds are difficult to break and hence the melting point of diamond is very high.

Fluorine halogens oxidizes water to oxygen exothermally.

Sulphur occurs in the earth’s crust in the combind state primarily in the form of sulphates and sulphides.

(i) As sulphates: Gypsum, (CaSO₄.2H₂O), Epsom salt (MgSO₄ 7H₂O), Baryte (BaSO₄) etc.

(ii) As Sulphides: Galena (PbS), Zine blende (ZnS), Copper pyrites (CuFeS₂), Iron pyrites (FeS₂) etc.

Traces of sulphur occur as H₂S and in organic matter such as eggs, proteins, onion, mustard, hair and wool etc.

(i) B(OH)₃ + 2HOH → [B(OH)₄ ]⁻ + H₃O⁺

(ii) 2NaBH₄ + I₂ → B₂H₆ + 2NaI + H₂

(iii) B₂H₆ (g) + 6H₂O(l) → 2B(OH)₃ (aq) + 6H₂ (g)

(iv) B₂H₆ + 3O₂ → B₂O₃ + 3H₂O

(v) 2BF₃ + 6NaH \(\overset{450K}{\rightarrow}\) B₂H₆ + 6NaF

(i) 2Al(s) + 6HCl(aq) → 2Al³⁺(aq) + 6Cl⁻(aq) + 3H₂(g)

(ii) Na₂B₄O₇ + 7H₂O → 2NaOH + 4H₃BO₃

(iii) Na₂B₄O₇ + 2HCl + 5H₂O → 2NaCl + 4B(OH)₃

(iv) 4BF₃ + 3LiAlH₄ → 2B₂H₆ + 3LiF + 3AlF₃

(v) 3B₂H₆ + 6NH₃ → 3[BH₂(NH₃)₂] +[BH₄]⁻ \(\overset{\Delta}{\rightarrow}\) 2B₃N₃H₆ + 12H₂

It is because bond dissociation energy of S – H bond is less than O – H bond due to longer bond length.

HClO₄ is more acidic.

When XeF₆ reacts with 2.5 M NaOH gives Na₄XeO₆.

When carbon monoxide is treated with chlorine in presence of light or charcoal, it forms a poisonous gas carbonyl chloride, when is also known as phosgene.

CO + Cl₂ ⟶ COCl₂

On industrial scale carbon monoxide is produced by the reaction of carbon with air. The carbon monoxide formed will contain nitrogen gas also and the mixture of nitrogen and carbon monoxide is called producer gas.

2C + O₂ /N₂(air) ⟶ 2CO + N₂

(i) Preparation of water gas and producer gas-

(a) C(s) + H₂O(g) → CO(g) + H₂(g)

(b) 2C(s) + O₂ + 4N₂ (g) → 2CO(g) + 4N₂ (g) (Producer gas)

Water gas and producer gas are used as fuel.

(ii) (a) Ca(OH)₂ + CO₂ → Ca(HCO₃)₂ (Soluble)

(ii) (a) Ca(OH)₂ + CO₂ → Ca(HCO₃)₂ (Soluble)

White (yellow) phosphorous glows in the dark due to oxidation which is called phosphorescence.

(c) four

There are two 3c – 2e^- bonds i.e., the bonding in the bridges account for 4 electrons.

CO is important for photosynthesis.

General empirical formula of silicone is (R₂SiO)

(d) (SiO₄)^4-

(c) sp² hybridised

Wade’s rules are used to rationalize the shape of borane clusters by calculating the total number of skeletal electron pairs (SEP) available for cluster bonding.

The atomic radius of boron is very small and it has relatively high nuclear charge and these properties are responsible for its non-metallic character.

The halogens have a strong tendency to gain an electron to give a stable halide ion with completely filled electronic configuration (ns₂sp₆) and hence-1 oxidation state is more common in halogens

(a) +4

CH₄⁺ in which the oxidation state of carbon is 4.

Carbon has a greater tendency to form a chain of bonds with itself.

More common oxidation state for halogens is -1.

(d) (iii) only

(b) stable electronic configuration

Electronic configuration of noble gases is ns²np⁶.

The elements of group-18 have completely filled s and p orbitals, hence they are more stable and have least reactivity. Therefore group-18 elements are called inert gases. ns₂np₆ is the general electronic configuration of group elements.

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

(i) – (c) 

(ii) – (d) 

(iii) – (b) 

(iv) – (a)

(i) – (b) (ii) – (a) (iii) – (d) (iv) – (c)

1. silicones

2. constant 

3. Silicones 

4. six oxygen 

5. Asbestos 

6. [SiO₄]^4- ; [AlO₄]^5-

7. Zeolite

8. tetraboric acid

(i) – (c) 

(ii) – (d) 

(iii) – (b) 

(iv) – (a)