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The correct answer is- (d) CCl₄

The correct option is- (b) 1.20Å

The correct option is- (a) N₂

The correct option is -(b) C₂H₄

The correct option is- (c) H₂

1. The polarity of a covalent bond can be measured in terms of dipole moment which is defined as: 

µ = q x 2d, where µ is the dipole moment, q is the charge, 2d is the distance between the two charges.

2. The dipole moment is a vector quantity and the direction of the dipole moment points from the negative charge to positive charge.

3. The unit of dipole moment is Coulomb metre (C m). It is usually expressed in Debye unit (D).

4. 1 Debye = 3.336 x 10^-30 Cm

Atoms are held together in chemical compounds due to chemical bonds.

Formal charge is the charge assigned to an atom in a molecule, assuming that all electrons are shared equally between atoms, regardless of their relative electronegativities.

Structure (I) :

Structure (II) :

Structure (III) :

While determining the best Lewis structure per molecule, the structure is chosen such that the formal charge is as close to zero as possible. 

The structure having the lowest formal charge has the lowest energy.

In structure (I),

The formal charge on each atom is 0 while in structures (II) and (III) formal charge on carbon is 0 while oxygens have formal charge -1 or +1. 

Hence, 

The possible structure with the lowest energy will be structure (I). 

Thus,

Formal charges help in the selection of the lowest energy structure from a number of possible Lewis structures for a given species.

The correct answer is- (c) CaF₂

1. The complete transfer of electrons leads to the formation of a cation and an anion. Both these ions are held together by electrostatic attractive forces which is known as ionic bond.

2. KCl: Potassium chloride

Electronic configuration of K[Ar] 4s

Eleçtronic configuration of Cl = [N]3s²3p⁵

3. Potassium has 1 electron in its valence shell and chlorine has 7 electrons in its valence shell.

4. By losing one electron potassium attains the nearest inert gas configuration of Argon and becomes a unipositive cation (K) and chlorine accepts this electron to become uninegative chloride ion (CI) to attain the stable configuration of nearest noble gas, Argon.

5. These two ions combine to form an ionic crystal in which they are held together by electrostatic attractive forces.

6. During the formation of one mole of potassium chloride crystal from its constituent ions, 718 kJ of energy is released. This favours the formation of KCl and its stabilisation.

1. Bond order \(\propto\) \(\frac{1}{Bond\,length}\)

2. An example for illustrating the above equation is Carbon – carbon single bond length (I .54Å) is longer than the carbon-carbon double bond length (1.34Å) and the carbon- carbon triple bond length (1 .20Å).

Covalent bonds are directional in nature and are oriented in specific direction in space. This directional nature creates a fixed angle between two covalent bonds in a molecule and this angle is termed as bond angle.

The similar structures in which the relative position of the atoms are same but they differ in the position of bonding and lone pair of electrons are called resonance structures and this phenomenon is called resonance.

(b) CO₂ . 

It contains covalent bond whereas others have ionic bond.

There are 9 σ-bonds and 2π-bonds.

(i) C₇H₈  15σ and 3π

(ii) C₆H₅OH  13σ and 3π

(iii) CH₃ - CH = C = CH - C ≡ CH  11σ and 4π

The Lewis concept of describe the formation of bond in terms of sharing of one or more electron pairs and the octet rule. It does not explain the energetic of the bond formation and shapes of the polyatomic molecules.

The VB theory describes the bond formation in terms of hybridization and overlap of the orbitals. The overlap of orbitals along the intermolecular axis increases the electron-density between the two nuclei resulting in a decrease in the energy and formation of a bond.

In Lewis concept, bond formation is explained in terms of sharing of electron pairs and the Octet rule whereas in VBT bond formation is described in terms of hybridization and overlap of the orbitals.

metal ions

Malleability and ductility of metals can be accounted due to the capacity of layers of metal ions to slide over one another.

In O-Nitrophenol there exists intra molecular hydrogen bonding within the molecule where as in p-nitrophenol there exists inter molecular hydrogen bonding between the molecule.

p-nitrophenol, is associated through intermolecular H-bonding and hence less volatile.

MgO has higher value of lattice energy due to stronger force of attraction between divalent Mg²⁺ and O^2- than monovalent Na= and Cl^- ions.

Atoms – ‘X’

1. Electrically – neutral particles

2. May or may not exist – independently

3. Outermost shell – may or may not have duplet or octet.

Ions – X¹⁺

1. Electrically-charged particles [cations, anions]

2. Exist – independently in solution

3. Outermost shell -have complete duplet or octet.

1. Sodium atom is neutral whereas sodium ion has unipositive charge. 

2. The size of sodium ion is smaller than sodium atom. 

3. The properties of sodium ion is different when compared with sodium.

The bond in XY₂ is ionic.

Properties:

(i) It is hard and brittle.

(ii) It is soluble in water.

(iii) It has high melting and boiling point.

(iv) It does not conduct electric current in the solid state but conducts electric current in the molten or dissolved state.

Two electrons are transferred from X to Y. X forms positive ion and Y forms a negative ion. So the bond formed is ionic in nature. 

Properties of ionic compounds : 

a) They are hard crystals. 

b) They have high boiling point and melting point. 

c) They are soluble in water.

Ionic compounds are generally formed between metals and non-metals as metals always lose  electrons to form cations while non-metals gain electrons forming anions to complete their octet.  These oppositely charged ions are held together by electrostatic force of attraction and hence  results in an ionic compound.

Correct Option is : (A) isoelectronic species and bond order 3

Both CO and \(NO^+\) have 14 electrons . It means they are isoelectronic species.

Both species have bond order = 3

Option : (A) isoelectronic species and bond order 3

The correct answer is (i) BH₄^–

In water, the central oxygen atom is sp³? hybridised whereas inCO₂, the central carbon atom issp-hybridised. Net dipole moment of CO₂  is zero whereas H₂O has a considerable value. This shows CO₂ is linear whereas water has bent structure.

The covalent molecules are held very weakly by van der Waal’s forces. Thus, there are large inter molecular spaces between the molecules. In other words the number of molecules per unit volume is less. Thus mass per unit is also less and hence, covalent compound have low density. 

The force of attraction between the molecules is very weak and so the amount of energy needed to separate them is small, consequently they have low melting points and boiling points. 

As the bond is formed by sharing of electrons between two atoms. Intermolecular forces are small between the covalent compounds. These bonds break easily.

They are covalent compounds.

1. The melting point is low due to the weak Vander Waal’s forces of attractions between the covalent molecules. 

2. The force of attraction between the molecules of a covalent compound is very weak. 

3. Only a small amount of heat energy is required to break these weak molecular forces, due to which covalent compounds have low melting points and low boiling points. 

4. Please note that some of the covalent solids like diamond and graphite have, however very high melting points and boiling points.

Coordinate Bond: It is a type of covalency which involves one of the combining atoms contributing both of the shared electrons, i.e. a bond formed by a shared pair of electrons with both electrons coming from the same atom.

Covalent compounds exhibit low melting and boiling points when compared to ionic compounds.

Fe (s) + CuSO₄ (aq) → FeSO₄ (aq) + Cu (s) 

Ionic equation for the reaction can be written as ;

Fe (s) + Cu²⁺ (aq) → Fe²⁺ (aq) + Cu (s)

In this reaction iron loses two electron and is oxidized to Fe²⁺ .

Fe (s) → Fe²⁺ (aq) (-2e^– ) (Oxidation)

On the other hand Cu²⁺ gains two electrons and is reduced to copper.

Cu²⁺ (aq) → 2e^– → Cu (s) (Reduction)

Thus the given reaction is a redox reaction.

The tendency of atoms to have eight electrons in the valence shell is known as the ‘Octet rule’ or the ‘Rule of eight’.

Example: Sodium with atomic number 11 will readily loose one electron to attain Neon’s stable electronic configuration

Covalent compounds exists as gases, liquids or soft solids because they have weak forces of attraction between their molecules. 

All the elements differ with each other in their valence shell electronic configuration. So the way in which they combine to form compounds also differs. Hence, there are different types of chemical bonding possible between atoms which make the molecules. Depending on the type of bond they show different characteristics or properties. Such types of bonding that are considered to exist in molecules are categorized as the Ionic bond, Covalent bond and Coordinate bond. 

Pure covalent bond exists between two elements which have similar electro negativities. In hydrogen chloride, chlorine being more electro negative attracts the shared pair of electrons towards itself. As a result hydrogen acquires partial positive charge and chlorine gets partial r negative charge. Thus, hydrogen chloride can be termed as a polar covalent compound.

Ions are charged particles.

The atom which loses electron acquire positive charge and the atoms gain electrons acquire a negative charge.

2. It is hard and brittle

(B) A low (m.p.) melting point and low (b.p.) boiling point

The formation of ionic compounds involves the formation of ions and the attraction of ion pairs.

1. It is an Oxidation reaction. 

Oxidation: A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electrons is called oxidation. 

2. It is a Reduction reaction.

 Reduction: A chemical reaction which involves addition of hydrogen or removal of oxygen or gain of electrons is called reduction.

(1) Oxidation

(2) Reduction

(3) Reduction

(4) Oxidation

Oxidation reactions: 

(3)  Sn⁴⁺ + 2e^–  → Sn²⁺

(6)  X + 2e^– → X^2-

(7)  Y - Ie^– → Y¹⁺

(8)  Z³⁺ + Ie^–  →  Z²⁺

 Reduction reactions.

(1) Cu → Cu²⁺ + 2e^–

(2)  Cu²⁺ + 2e^– → Cu 

(4)  2Cl^- → Cl₂ + 2e^-

(5)  Fe²⁺ → Fe³⁺ +  Ie^– 

Oxidation: Loss of one or more electrons by an atom or ion is called oxidation.

For example,

Na → Na⁺ + e^–

Fe²⁺ → Fe³⁺ + e^-

Mg → Mg²⁺ + e^-

Reduction: Gain of one or more electrons by an atom or ion is called reduction.

For example,

F + e^– → F^–

O + 2e^- → O^2–

Cu²⁺ + e^– → Cu⁺

Zn² + 2^e– → Zn