Question

which molecule is an example of a non-polar molecule?
a. ammonia (nh₃)
b. water (h₂o)
c. hydrogen chloride (hcl)
d. methane (ch₄)

Explanation:

To determine a non - polar molecule, we analyze the molecular geometry and electronegativity differences:

• Ammonia ($\ce{NH_3}$) has a trigonal pyramidal shape. The nitrogen - hydrogen bonds are polar, and the molecular geometry doesn't cancel out the dipole moments, so it is polar.
• Water ($\ce{H_2O}$) has a bent shape. The oxygen - hydrogen bonds are polar, and the bent geometry means the dipole moments don't cancel, making it polar.
• Hydrogen chloride ($\ce{HCl}$) is a diatomic molecule with a polar covalent bond (due to the electronegativity difference between H and Cl), so it is polar.
• Methane ($\ce{CH_4}$) has a tetrahedral geometry. The carbon - hydrogen bonds have a relatively small electronegativity difference, and the symmetric tetrahedral shape causes the dipole moments of the individual bonds to cancel out, resulting in a non - polar molecule.

Answer:

d. Methane ($\ce{CH_4}$)