Question:

Which of the following orders are correct against the property given? I) dipole moment : NF3>NH3>BF3NF_3 > NH_3 >BF_3 II) Covalent bond length : CO>NO>OHC - O > N - O > O - H III) Bond order : C2>B2>He2C_2 > B_2 > He_2

Updated On: Apr 2, 2024
  • I, II only
  • II, III only
  • I, III only
  • I, II , III
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The Correct Option is B

Solution and Explanation

(I) In BF3BF _{3}, electronegativity of FF -atom is greater than BB.



In NH3NH _{3}, electronegativity of NN -atom is greater than HH. Therefore, direction of all dipole moment with lone pairs lies in same direction, hence net dipole moment increases.



In NF3NF _{3}, electronegativity of FF is greater than NN. Therefore, direction of dipole moment are opposite from the lone pair, hence, net dipole decreases.



Correct order of dipole moment will be

NH3>NF3>BF3NH _{3}>\, NF _{3}>\, BF _{3}

(II) Covalent bond length

CO>NO>OHC - O > \,N - O >\, O - H

as electronegativity difference increases then bond length decreases but lone pair-lone pair repulsion increases the bond length.

(III ) Bond order = Number of bonding electron (Nb)\left(N_{b}\right)
 - Number of antibonding electron 2\frac{\text { - Number of antibonding electron }}{2}

$C _{2}=\sigma l s^{2}
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Concepts Used:

Bond Parameters

Covalent bonds can be characterized on the basis of several bond parameters such as bond length, bond angle, bond order, and bond energy (also known as bond enthalpy). These bond parameters offer insight into the stability of a chemical compound and the strength of the chemical bonds holding its atoms together.

Bond parameters 

  • Bond length: it is an equilibrium distance between the centres of the nuclei of the two bonded atoms. It is expressed in terms of A.
  • Bond Angle: It is characterized as the point between the orbitals consisting of holding electron sets around the focal iota in an atom/complex particle. Bond points are communicated in degrees which are tentatively controlled by spectroscopic strategies.
  • Bond Enthalpy: the measure of energy needed to break one mole of obligations of a specific sort between two molecules in a vaporous state. The unit of bond enthalpy is kJ mol–1. The more the bond enthalpy, the more grounded the bond is.

For example, The H—H bond enthalpy in hydrogen is 435.8 kJ mol-1. \

  • Bond Order: According to Lewis, Bond Order is given by the number of connections between the two atoms in a particle.

Bond order of H2 (H —H) =1
Bond order of 02 (O = O) =2
Bond order of N2 (N = N) =3

  • Resonance Structures: It is observed that there are many molecules whose behaviour cannot be explained by a single Lewis structure.

Read More: Chemical Bonding and Molecular Structure