Which one of the following is an oxidation reduction reaction?

An oxidation-reduction (redox) reaction involves the transfer of electrons, resulting in changes to the oxidation states of the reactants [4]. In the reaction 2Mg + O2 → 2MgO, magnesium (Mg) is oxidized as it gains oxygen and loses electrons to form Mg²⁺, while oxygen (O2) is reduced as it gains electrons [2]. This specific process is a combination reaction where magnesium burns in air to form magnesium oxide [2]. In contrast, the other options represent different chemical processes: NaOH + HCl is a neutralization reaction between an acid and a base [3]; CaO + H2O is a combination reaction forming slaked lime without oxidation state changes [1]; and Na2SO4 + BaCl2 is a double displacement (precipitation) reaction where ions are simply exchanged to form insoluble barium sulfate [3]. Therefore, only the magnesium reaction satisfies the redox criteria.

Sources

1. [4] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > 2.1.4 How do Acids and Bases React with each other? > p. 21
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > CuO +H Cu+H O 2 2 → Heat (1.29) > p. 13
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > QUESTIONS > p. 7
4. [1] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > CuO +H Cu+H O 2 2 → Heat (1.29) > p. 12