4.
Which of the following molecules will have a dipole moment?
a. CH4
b. NH3
c. CCl4
d. CO2

Which Molecules Have Dipole Moment: CH4, NH3, CCl4, CO2 Explained

NH3 is the only molecule with a net dipole moment among CH4, NH3, CCl4, and CO2 due to its asymmetrical shape. The correct answer is option b. NH3.​

Option Analysis

CH4 (Methane): CH4 has a tetrahedral geometry with four identical C-H bonds. Electronegativity differences create individual bond dipoles, but perfect symmetry causes them to cancel completely, resulting in zero net dipole moment.​

NH3 (Ammonia): NH3 exhibits trigonal pyramidal shape from sp3 hybridization and a lone pair on nitrogen. Polar N-H bonds and the lone pair’s dipole reinforce each other, producing a net dipole moment of about 1.5 D.​

CCl4 (Carbon Tetrachloride): CCl4 features tetrahedral symmetry with four C-Cl bonds. Despite polar bonds due to chlorine’s higher electronegativity, vector sum of dipoles cancels out, yielding zero net dipole moment.​

CO2 (Carbon Dioxide): CO2 adopts linear geometry (O=C=O) from sp hybridization. Two polar C=O bonds have equal magnitude but opposite directions, canceling to zero net dipole moment.​​

Which molecules have dipole moment among CH4, NH3, CCl4, CO2? This common CSIR NET question tests VSEPR theory and polarity basics. NH3 alone exhibits a net dipole due to its trigonal pyramidal structure, while symmetrical CH4, CCl4, and linear CO2 cancel out.​

Dipole Moment Basics

Dipole moment ($\mu =q\times d$) measures charge separation in molecules. It depends on bond polarity (electronegativity difference) and geometry. Symmetrical shapes yield zero $\mu$; asymmetry creates net polarity.​

Detailed Breakdown

• CH4: Tetrahedral, symmetric; $\mu =0$.​

• NH3: Pyramidal, lone pair effect; $\mu >0$.​

• CCl4: Tetrahedral, symmetric; $\mu =0$.​

• CO2: Linear, symmetric; $\mu =0$.​