What is the approximate change in the HCH bond angle in ethene when it reacts with chlorine to form

Question

What is the approximate change in the HCH bond angle in ethene when it reacts with chlorine to form 1,2-dichloroethane?

Professor PC Thomas Classes · Answer

Ethene ($sp^2$) angle is $\sim 120^\circ$. 1,2-dichloroethane ($sp^3$) angle is $\sim 109.5^\circ$. Difference is $\approx 10.5^\circ$ (closest to $11^\circ$).