A Level Chemistry OCR Practice Exam

Which process involves breaking a covalent bond by evenly sharing electrons?

1. Heterolytic fission.

2. Homolytic fission.

3. Heterogeneous catalysis.

4. Electrophilic addition.

The correct answer is: Homolytic fission.

Homolytic fission is the process where a covalent bond is broken evenly, resulting in the formation of two free radicals. In this process, each atom involved in the covalent bond retains one of the shared electrons, leading to two particles with unpaired electrons. This is significant in organic chemistry, particularly in reactions where free radicals are formed, like in chain reactions. In contrast, heterolytic fission involves breaking a covalent bond in such a way that one atom takes both electrons from the bond, creating a positively charged ion and a negatively charged ion. Heterogeneous catalysis refers to a process where a catalyst exists in a different phase from the reactants, facilitating a chemical reaction without the formation of free radicals, and electrophilic addition involves a reactive electrophile adding to a nucleophile, which does not entail the creation of radicals through the even sharing of electrons. Therefore, the concept of evenly sharing electrons is exclusively associated with homolytic fission.