Which of the following involves a transfer of electrons? PCl3 + Cl2 → PCl5 CO2 + 2LiOH → Li2CO3 + H2O FeCl2 + 2NaOH → Fe (OH) 2 + 2NaCl NaOH + HCl → NaCl + H2O

Answer is: PCl3 + Cl2 → PCl5.

Balanced chemical reaction: PCl₃ + Cl₂ → PCl₅.

Oxidation half reaction: P⁺³ → P⁺⁵ + 2e⁻.

Reduction half reaction: Cl₂ + 2e⁻ → 2Cl⁻.

In this chemical reaction phosphorus lost two electrons and change oxidatation number from + 3 to + 5; chlorine gain those two electrons and change oxidation number form 0 to - 1.

In other chemical reactions, elements do not change oxidation numbers.