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Practice each question, then open the answer or worked solution.
Explain the important aspects of resonance with reference to the CO32− ion.
Experimental results shows that, all the C-O bond in
Thus, it is inefficient to represent
Thus, the resonance structures of
H3PO3 can be represented by structures 1 and 2 shown below. Can these two structures be taken as the canonical forms of the resonance hybrid representing H3PO3? If not, give reasons for the same.
In the given structures, the position of atoms is changed, so we cannot take the 2 given structures as a canonical form of resonance hybrid which represents H3PO3.
Write the resonance structures for SO3, NO2, and NO3–.
SO3
NO2
Use Lewis symbols to show electron transfer between the following atoms to form cations and anions :
(i) K and S
(ii) Ca and O
(iii) Al and N.
(i) K and S
Electronic configurations of S and K are:
S: 2, 8, 6
K: 2, 8, 8, 1
Here, it is clear that K has 1 more electron than the nearest inert gas, i.e., Ne, whereas S needs 2 electrons to complete its octet. Thus, the transfer of electrons takes place in the following way,
(ii) Ca and O
Electronic configurations of O and Ca are:
O: 2, 6
Ca: 2, 8, 8, 2
Here, it is clear that Ca has 2 more electrons than the nearest inert gas Ar, whereas O needs 2 electrons to complete its octet. Thus, the transfer of electrons takes place in the following way,
(iii) Al and N
Electronic configurations of N and Al are:
N: 2, 5
Al: 2, 8, 3
Here, it is clear that Al has 3 more electrons than the nearest inert gas Ne, whereas N needs 3 electrons to complete its octet. Thus, the transfer of electrons takes place in the following way,
Although both CO2 and H2O are triatomic molecules, the shape of the H2O molecule is bent while that of CO2 is linear. Explain this on the basis of dipole moment.
Experimental results show that the dipole moment of CO2 is 0. And it is possible only if the shape of the molecule is linear as dipole moments of a bond between C-O are equal and opposite. So, it nullifies each other.
H2O has 1.84 D dipole moment. The value of dipole moments indicates that the structure of water molecule is bent as dipole moments of the bond between O-H are unequal.
Write the significance/applications of dipole moment.
The following are some of the key significance of the dipole moment:
Define electronegativity. How does it differ from electron gain enthalpy?
“Electronegativity is the ability of an atom in a chemical compound to attract a bond pair of electrons towards itself”.
| Sr. No | Electronegativity | Electron affinity |
| 1 | A tendency to attract the shared pairs of electrons for an atom which is in a chemical compound is its electronegativity. | A tendency to gain electrons for an isolated gaseous atom is its electron gain enthalpy. |
| 2 | It varies according to the element with which it is bounded. | It does not vary according to the element with which it is bounded. |
| 3 | It is not constant for any element. | It is constant for an element. |
| 4 | It is not a measurable quantity. | It is a measurable quantity. |
Explain with the help of suitable example polar covalent bond.
When two unique atoms having distinct electronegativities join to form a covalent bond, the bond pair of electrons are not shared equally. The nucleus of an atom having greater electro-negativity attracts the bond pair. So, the electron distribution gets distorted and an electronegativity atom attracts the electron cloud.
Thus, the electronegative element gets slightly negatively charged and on the other hand, the other atom gets slightly positively charged. As a result of this, two opposite poles are developed in a molecule, and this type of bond formed is termed a ‘polar covalent bond’.
E.g. HCl is having a polar covalent bond. In HCl, Cl- atom has more electronegativity than H- atom. Thus, bond pair shifts towards Cl- atom and because of that, it acquires a positive charge.
Arrange the bonds in order of increasing ionic character in the molecules: LiF, K2O, N2, SO2, and ClF3.
The ionic character of a molecule depends on the difference in electronegativity between constituents atoms. So, the higher the difference is, the higher the ionic character of a molecule will be.
So, the required order of ionic character of the given molecules is
N2< SO2< ClF3< K2O <LiF.
The skeletal structure of CH3COOH as shown below is correct, but some of the bonds are shown incorrectly. Write the correct Lewis structure for acetic acid.
Correct Lewis structure of CH3COOH is given below:
