Question

The molecule having zero dipole moment is:
A. $CHC{l_3}$
B. ${H_2}O$
C. $CC{l_4}$
D. $HCl$

Answer 1

Hint: To solve this question, we must first understand some basic concepts about Dipole moment and polarity. Then we need to use the concept of polarity and direction of dipole moment to determine the net dipole moment of each of the given compounds and then only we can conclude the correct answer.

Complete answer:
Before we move forward with the solution of this given question, let us first understand some basic concepts:
- Polarity is the property of an object to possess opposite physical properties at different points. Physical properties can be magnetic properties or electrical charge.
- A molecule is said to be polar if one of the atom or group of atoms has the tendency to attract electrons towards itself(electronegative) thereby, getting a complete or partial negative charge on itself and a complete or partial positive charge will be generated on the atom or group of atoms to which the former is bonded to. For example, $HCl$ or water.
- A bond dipole moment uses the concept of electrical dipole moment in order to measure the extent of polarity of a chemical bond between two atoms of a molecule.
- A molecule is said to have zero dipole moment if the opposite dipole moments cancel each other or there are no partial charges present on the opposite ends of a covalent bond.
Step 1: $CHC{l_3}$: It​ has a perfect tetrahedral geometry but due to the presence of dissimilar groups, its net dipole moment is not zero.
Step 2: ${H_2}O$: It has a bent structure with a non-zero dipole moment.
Step 3: $CC{l_4}$​: It has a perfect tetrahedral geometry with all side atoms the same.
Due to symmetry, this molecule has a net zero dipole moment.
Step 4: $HCl$: It is a diatomic molecule with dissimilar atoms. Due to the difference in electronegativities of the 2 atoms.
Hence we can conclude that the only compound with zero dipole moment is $CC{l_4}$.

So, clearly we can conclude that the correct answer is, ‘C. $CC{l_4}$’

Note: A dipole moment is a quantity that describes two opposite charges separated by a distance. It is a quantity that we can measure for a molecule in the lab and thereby determine the size of the partial charges on the molecule (if we know the bond length).