Chemical Bonding And Molecular Structure

Statements:

1. is prepared by the reaction of white phosphorus with excess of dry chlorine.
2. The complete hydrolysis of gives phosphoric acid.
3. has square pyramidal structure in gaseous phase.
4. All the five bonds in molecule are equivalent.

Correct Answer: i and ii

Explanation:

• Statement (i) is correct: White phosphorus reacts with excess dry chlorine to form phosphorus pentachloride.
• Statement (ii) is correct: Complete hydrolysis of gives phosphoric acid ( ).
• Statement (iii) is incorrect: has a trigonal bipyramidal geometry in gaseous and liquid phases, not square pyramidal.
• Statement (iv) is incorrect: In the trigonal bipyramidal structure, the axial and equatorial bonds are not equivalent.

Which one of the following is true?

• Chemisorption is not specific in nature
• Physisorption is irreversible
• Both physisorption and chemisorption depend on the nature of the gas
• Enthalpy of adsorption is high in physisorption
• Chemisorption increases with surface area of adsorbent while in physisorption it is not

Correct Answer: Both physisorption and chemisorption depend on the nature of the gas

Explanation:

• Physisorption involves weak van der Waals forces and is influenced by the polarisability of the gas.
• Chemisorption depends on the ability of the gas to form a chemical bond with the surface, so it is also gas-specific.

Incorrect Statements:

• Chemisorption is specific because it involves chemical bond formation.
• Physisorption is usually reversible, not irreversible.
• Physisorption has low enthalpy change (~20–40 kJ/mol), while chemisorption has high enthalpy (~80–200 kJ/mol).
• Both types of adsorption increase with surface area of adsorbent.

The octet rule states that atoms in molecules tend to have eight electrons in their valence shell, like the noble gases. However, some molecules do not follow this rule.

SF : Sulfur has more than eight electrons in its valence shell, as it is able to accommodate more than eight electrons due to the availability of d-orbitals.

AlCl : Aluminum in AlCl only has six electrons in its valence shell, which is an example of an incomplete octet, meaning it does not satisfy the octet rule.

CH : Carbon in CH follows the octet rule as it shares four electrons with four hydrogen atoms, completing its octet.

PF : Phosphorus in PF has ten electrons in its valence shell, which is allowed as phosphorus can expand its octet.

H O: Oxygen in H O has eight electrons in its valence shell, fulfilling the octet rule.

Thus, the molecule AlCl contains an incomplete octet of the central atom.

The correct option is (B) :

Let's calculate the number of oxygen atoms in each compound:
Aluminum Sulphate (Al (SO ) ): One mole of aluminum sulphate contains 3 moles of sulphate ions (SO ), and each sulphate ion contains 4 oxygen atoms. Therefore, one mole of aluminum sulphate contains:
Ferrous Sulphate (FeSO ): Each mole of ferrous sulphate contains 1 mole of sulphate ions (SO ), and each sulphate ion contains 4 oxygen atoms. Therefore, two moles of ferrous sulphate contain:
Hydrogen Peroxide (H O ): One mole of hydrogen peroxide contains 2 moles of oxygen atoms. Therefore, three moles of hydrogen peroxide contain:
Potassium Permanganate (KMnO ): Each mole of potassium permanganate contains 4 moles of oxygen atoms. Therefore, two moles of potassium permanganate contain: - Potassium Dichromate (K Cr O ): Each mole of potassium dichromate contains 7 moles of oxygen atoms. Therefore, one mole of potassium dichromate contains: Thus, one mole of aluminum sulphate contains the highest number of oxygen atoms, with 12 moles of oxygen atoms. The correct answer is (1) One mole of aluminum sulphate.

The correct option is (A) : One mole of aluminum sulphate

Saline hydride (a): This is a hydride formed by a metal (usually alkali or alkaline earth metals) reacting with hydrogen. The typical example is BeH₂, which is (iii).
Electron-deficient hydride (b): These are hydrides where the central atom does not have a complete octet, such as B₂H₆, which is (iv).
Electron-precise hydride (c): These hydrides have a perfect balance of electrons, like CH₄ (methane), which is (ii).
Electron-rich hydride (d): These are hydrides where the central atom has more than an octet of electrons, like H₂O (water), which is (v).
Metallic hydride (e): These hydrides are formed by transition metals, typically with the formula CrH, which is (i).

The correct option is (D) : a)-(iii); b)-(iv); c)-(ii); d)-(v); e)-(i)

S₈ molecule structure:

• Crown-shaped cyclic molecule with 8 sulfur atoms
• Each S atom forms 2 S-S bonds (total 8 bonds in ring)
• Each S atom has 2 lone pairs (total 16 lone pairs)

Thus, the correct option is (B): 8, 16.

sp-hybridized carbon identification:

• (A) CH₃-CH=CH-CH₃: sp² hybridized (alkene)
• (B) CH₃-C≡C-CH₃: sp hybridized (alkyne)
• (C) CH₃-CH₃: sp³ hybridized (alkane)
• (D) CHCl₃: sp³ hybridized
• (E) CH₃-CH₂-Cl: sp³ hybridized

Thus, the correct option is (B): CH₃-C≡C-CH₃.

XeOF₄ VSEPR analysis:

• Central Xe with 5 bond pairs (4 F + 1 O) and 1 lone pair
• AX₅E configuration (octahedral electron geometry)
• Lone pair occupies axial position → Square pyramidal molecular shape

Thus, the correct option is (A): Square pyramid.

Step 1: The octet rule states that atoms tend to form bonds in such a way that they achieve a stable electron configuration with 8 valence electrons. Step 2: In (Sulfur dichloride), sulfur forms two single bonds with chlorine, fulfilling its octet requirement (6 valence electrons + 2 shared electrons = 8).
Step 3: The other molecules: - and have expanded octets.
- does not complete the octet (Boron has only 6 valence electrons).
- involves delocalized bonding and resonance.
Step 4: Since only strictly follows the octet rule, the correct answer is (A).

Step 1: Sigma ( ) bonds are single bonds, while pi ( ) bonds are additional bonds in double or triple bonds.
Step 2: Analyzing each molecule:
has 1 and 2 bonds.
has only bonds.
has only bonds.
has a triple bond between C and N, meaning 1 and 2 bonds between them. Additionally, a bond exists between H and C.
has different bonding but does not match the criteria.
Step 3: Since HCN has exactly 2 sigma bonds and 2 pi bonds, the correct answer is (D).

Hydrogen bonding occurs when a hydrogen atom is directly bonded to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F).
Let's analyze the options:
- Phenol: The hydroxyl group (-OH) contains hydrogen bonded to oxygen, which can form hydrogen bonds.
- Diethyl ether: The oxygen atom in diethyl ether is bonded to carbon atoms but does not have a hydrogen atom directly bonded to it, so it cannot form hydrogen bonds.
- Aniline: The amino group (-NH2) contains hydrogen bonded to nitrogen, allowing for hydrogen bonding.
Thus, the correct answer is .