• # question_answer Which bond angle $\theta$would result in the maximum dipole moment for the triatomic molecule $YXY$ [AIIMS 1980] A)                 $\theta ={{90}^{o}}$    B)                 $\theta ={{120}^{o}}$ C)                 $\theta ={{150}^{o}}$  D)                 $\theta ={{180}^{o}}$

The dipole moment of two dipoles inclined at an angle $\theta$ is given by the equation $\mu =\sqrt{{{X}^{2}}+{{Y}^{2}}+2XY\cos \theta }$ $\cos 90{}^\circ =0$. Since the angle increases from $90-180$, the value of $\cos \theta$ becomes more and more ? ve and hence resultant decreases. Thus, dipole moment is maximum when $\theta =90{}^\circ$.