Chemical BondinghardNUMERICAL

A triatomic molecule has an experimental resultant dipole moment exactly equal to the individual bonChemical Bonding Chemistry Question

Question

A triatomic molecule $AX_2$ has an experimental resultant dipole moment exactly equal to the individual bond moment of the $A-X$ bond ($\mu_R = \mu_{A-X}$). What is the $X-A-X$ bond angle in degrees?

Answer: 120

💡 Solution & Explanation

Using vector addition for two identical bonds: $\mu_R = \sqrt{\mu_{A-X}^2 + \mu_{A-X}^2 + 2\mu_{A-X}^2\cos\theta}$. Since $\mu_R = \mu_{A-X}$, we have $1 = \sqrt{1 + 1 + 2\cos\theta}$, which simplifies to $1 = 2 + 2\cos\theta$. $2\cos\theta = -1$, meaning $\cos\theta = -0.5$. Thus, $\theta = 120^\circ$.

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