Question

You and a friend are studying for a chemistry exam. What if your friend tells you that all molecules with polar bonds are polar molecules? How would you explain to your friend that this is not correct? Provide two samples to support your answer.

Short answer

Answer

The polarity of any covalent bond can be explained by the concept of dipole moment ($\mathrm{\mu }$), which is a vector quantity.

Step-by-step solution

Define dipole moment.

The product of charge and the distance by which charge is separated is known as the dipole moment.

$\mu =q\times d$

Where,

$\mu \to$dipole moment

$q\mathit{\to }$charge

$d\to$distance of separation

It is a vector quantity.

Use this concept to explain polarity.

Consider the example of the CO₂ molecule. It is a linear molecule. Even though the bond between C and O is polar, CO₂ is non-pole. It is because the individual bond moment cancels out each other.

Similarly, the bond between B and F is polar but BF₃ is non-polar. The resultant dipole moment of 2 bonds cancels out the 3^rd one.