Chemistry NCERT Exemplar Solutions Class 11th Chapter Four

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (iii)

The molecular orbital diagram of O₂^2-,   π^∗2Px and π^∗2Py molecular orbitals are completely filled, which are partially filled in O2. These are no unpaired electrons. So,  O₂^2-does not contain unpaired electrons.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (iii)

A double bond has one s bond and one π bond. In the above given structure 5π bonds are present. The s bonds are the additions of all the single bonds in the structure. There are 19s bonds in the above given structure.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (i)

(i) The molecule of BH₄ ^- has four bond pairs and zero lone pair of electrons, so it will be a tetrahedral molecule.

(ii) NH₂ ^- has two bond pairs and two lone pairs of electrons on the nitrogen atom. So, it will have a bent geometry.

(iii) CO₃ ^2- has three bond pairs and no lone pairs of electrons on carbon atoms. So, it will have a trigonal planar geometry.

(iv) H₃O⁺ has three bond pairs and one lone pair of electrons on oxygen atoms. So, it has a pyramidal geometry.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (iv)

The number of bond pairs on the nitrogen atom of NO₃^-  are 4 and the structure of - NO₃ does not have any lone pairs of electrons. The structure of  NO₃^- molecule is:

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (ii)

In a polyatomic molecule or an ion, the formal charge of an atom is defined as the difference between the valence electrons present in that atom and the number of electrons assigned to that atom in the Lewis structure.

Formal charge = No. of valence electrons - (No. of lone pair $+\frac{1}{2}Nbelectrons)$

Formal Charge = 6 - $\left(6+\frac{1}{2}*2\right)$

Formal Charge = -1

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (ii)

The size and the electronegativity are the main factors on which the strength of a compound depends on. As the size of the atom decreases, the electronegativity increases and thus the hydrogen-bonding becomes stronger. Thus, the strength of hydrogen-bonding in the given compounds is: H₂O > HF > NH₃

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (ii)

The hybrid orbitals of nitrogen in the given species will be confirmed by knowing the hybridization. In  NO₂⁺ the central nitrogen atom is sp hybridized as it has a linear shape. The molecule NO₃^- is sp²  due to the presence of one lone pair of electrons on a nitrogen atom and hence having a bent geometry. The molecule NH₄⁺ is sp³  hybridized having a tetrahedral geometry.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (iii)

The dipole moment of the molecule depends on the difference in the electronegativity of the atoms present in the structure. The dipole moment of CO₂ is 0, HI is 0.38, H₂O is 1.84 and SO₂ is 1.62.

As the oxygen atom is highly electronegative and hydrogen is least electronegative, the difference in electronegativity will be the highest for water molecules. Therefore, water molecules will have the highest dipole moment.