Question

Which bond angle will result in maximum dipole moment for $X{Y}_2$?

• A. $\theta ={90}^{\circ }$
• B. $\theta ={120}^{\circ }$
• C. $\theta ={150}^{\circ }$
• D. $\theta ={180}^{\circ }$

Answer 1

The correct option is A

$\theta ={90}^{\circ }$

$X{Y}_2$ will be looking like Y-X-Y or Y = X = Y.

In both the arrangements, ${180}^{\circ }$ will result in cancellation and thus, no net dipole moment.

${\mu }_{net}=\sqrt{{\mu }_1^2+{\mu }_2^2+2{\mu }_1{\mu }_{2}cos\theta }$

Where $\theta$ is angle between the ligands(Y)

For $\theta ={90}^{\circ }\Rightarrow cos\theta =0$

$\theta ={120}^{\circ }\Rightarrow cos\theta =-0.5$

$\theta ={150}^{\circ }\Rightarrow cos\theta =-0.87$

for ${120}^{\circ }$ and ${150}^{\circ }$, it will result in the term $-2{\mu }_1{\mu }_{2}cos\theta$ which will reduce the magnitude of dipole moment,

Thus, at $\theta ={90}^{\circ }$, $\mu$ will have maximum value.