Question

Which bond angle $\left(\theta \right)$ would result in the maximum dipole moment for the triatomic molecule $X{Y}_2$

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

Answer 1

The correct option is A $\theta$ = ${90}^o$

The molecule consists of two atoms of $Y$ and one of $X$.
$\therefore X$ is the central atom.

The magnitude of net resultant dipole moments of two dipole moment vectors (${\mu }_1$ and ${\mu }_2$ ) is given by,

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

where, $\theta$ = angle between them.

At $\theta ={90}^o$, cos$\theta$ = 0
So, $\mu$ = maximum

From ${90}^o$ onwards, the value of cos $\theta$ will become negative, so the value of ${\mu }_{net}$ will start decreasing after ${90}^o$.
Hence, the value of bond angle (θ) that would result in the maximum dipole moment at $\theta$ = 90°