Question

The bond angle which would result in the maximum dipole moment for the tri-atomic molecule $X{Y}_2$ (shown above) is:

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

Answer 1

Answer: (A)

${90}^o$

Dipole moment, $\mu =\sqrt{{\mu }_1^2+{\mu }_2^2+2{\mu }_1{\mu }_{2}cos\theta }$.

Among the options given, a dipole will be maximum if $\theta ={90}^o$. Because $cos(90+\theta )<0$, cos is negative in II and III quarters. However, $cos\theta >0$ above ${180}^o$ in the IVth quarter.

Hence from the given angles, the bond angle is highest for $\theta ={90}^o$
Option A is correct.