Electron Sharing Reactions · Paper 1 — Free Chemistry HL Practice Questions

A molecule of $\text{CCl}_4$ has polar C–Cl bonds yet a zero net dipole moment. Which statement correctly explains this?

Elements X, Y, and Z have Pauling electronegativity values of $0.9$, $3.0$, and $3.5$ respectively. Which bond formed between a pair of these elements has the smallest electronegativity difference and is therefore closest to non-polar covalent?

Oxygen gas and nitrogen gas are both homonuclear diatomic molecules, yet they differ in bond order: $\text{O}_2$ has a bond order of 2 and $\text{N}_2$ has a bond order of 3. Which statement correctly describes the polarity and bond order of these molecules?

In ethene ($\text{C}_2\text{H}_4$), the carbon–carbon double bond consists of one $\sigma$ bond and one $\pi$ bond. During electrophilic addition of bromine ($\text{Br}_2$), the $\pi$ bond breaks preferentially. Which statement correctly explains why the $\pi$ bond is weaker and more reactive than the $\sigma$ bond?