Question

which of the following molecules is symmetrical and non-polar despite having polar bonds?

a. ammonia (nh₃)

b. carbon dioxide (co₂)

c. water (h₂o)

d. hydrogen chloride (hcl)

Explanation:

To determine the molecule that is symmetrical and non - polar despite having polar bonds, we analyze each option:

• Option a: Ammonia ($\ce{NH_3}$) has a trigonal pyramidal shape. The dipole moments of the $\ce{N - H}$ bonds do not cancel out, so it is polar.
• Option b: Carbon dioxide ($\ce{CO_2}$) has a linear structure with the formula $\ce{O = C = O}$. The two $\ce{C = O}$ bonds are polar, but due to the linear and symmetrical arrangement of the atoms around the carbon atom, the dipole moments of the two bonds cancel each other out. So, $\ce{CO_2}$ is non - polar and symmetrical.
• Option c: Water ($\ce{H_2O}$) has a bent shape. The dipole moments of the $\ce{O - H}$ bonds do not cancel out, making it a polar molecule.
• Option d: Hydrogen chloride ($\ce{HCl}$) is a diatomic molecule with a polar bond, and since it has only two atoms, there is no symmetry to cancel the dipole moment, so it is polar.

Answer:

b. Carbon dioxide ($\ce{CO_2}$)