Question

Estimate the percent ionic character of the HBr molecule, given that the dipole moment $(\mu )$ is 0.79D and HBr bond length 151 pm.
(A) 10.9
(B) 11
(C) 12
(D) 8.2

Answer 1

Hint: The quantity that describes two opposite charges separated by a distance is known as dipole moment. The measure of the polarity of a chemical bond between two atoms in molecules is known as a bond dipole moment.

Complete step by step answer:
-A dipole moment is the measure of the polarity of a chemical bond between two atoms in a molecule.
-The bond dipole moment is a vector quantity which means it has magnitude as well as direction.
-In a polyatomic molecule, the dipole moment of a single bond that is a bond dipole moment is different from the dipole moment of the molecule as a whole.
-The dipole moment being a vector quantity can also be zero as the two oppositely acting bond dipoles can cancel each other.
-The dipole moment is represented by the Greek letter $'\mu '$ .
-Mathematically, the dipole moment is the product of the magnitude of the charge and the distance between the centers of the positive and negative charges, that is
$\text{Dipole Moment(}\mu \text{)}=\text{ Charge}(Q)\times \text{Distance of separation(r)}$

-The unit of dipole moment is denoted by the letter D, where $1D=3.33564\times {{10}^{-30}}C.m$ (C is Colomb and m denotes a meter).
-Given the value of the dipole moment of the HBr molecule as 0.79D, which is the value of observed dipole moment.
-Now, calculating the dipole moment of the HBr molecule,
\[\mu =e\times 1=4.8\times {{10}^{-10}}esu\times 1.51\times {{10}^{-10}}cm=7.248\times {{10}^{-18}}\text{esu cm}\]

-Since we know that, $1Debye=3.33564\times {{10}^{-30}}C.m=1\times {{10}^{-18}}\text{esu cm=7}\text{.248Debye}$

-The observed value of the dipole moment of any molecule can be calculated using the following formula, $\text{Observed value of }\mu =\dfrac{\text{observed value }\times \text{100}}{\text{calculated value}}=\dfrac{0.79\times 100}{7.248}=10.9%$

So, the correct answer is “Option A”.

Note: Dipole moment may refer to different terms for the conditions. It can refer to the electric dipole moment which is the measure of the electrical polarity of a system of charges. It can refer to the transition dipole moment which is the electrical dipole moment in quantum mechanics. It can refer to the molecular dipole moment which is the electrical dipole moment of a molecule. It can refer to the bond dipole moment which is the measure of the polarity of a chemical bond. It can refer to the electron electric dipole moment which is the measure of the charge distribution within an electron. It can also refer to the magnetic dipole moment which is the measure of the magnetic polarity of a system of charges.