Question

Which bond angle $\theta$ would result in the maximum dipole moment for the triatomic molecule $X{Y}_2$ as shown below?

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

Answer 1

Answer: (A)

The dipole moment of two dipoles inclined at an angle $\theta$ is given by the equation,

$\mu =\sqrt{X^2+Y^2+2XY\cos \theta }$

$\cos 90^{\circ }=0$. As the angle increases from $90^{\circ }$ to $180^{\circ }$, the value of $\cos \theta$ becomes more and more $-$ ve and hence resultant decreases. Thus, dipole moment is maximum when $\theta =90^{\circ }.$