Which one of the following statements regarding oxidation and reduction reactions is NOT correct ?

In chemical reactions, oxidation and reduction are defined by the transfer of oxygen and hydrogen. Oxidation is characterized by the gain of oxygen or the loss of hydrogen [3]. Conversely, reduction is defined as the loss of oxygen or the gain of hydrogen [3]. Therefore, if a substance loses hydrogen during a reaction, it is being oxidized, not reduced [3]. This makes statement 1 incorrect. Statements 2, 3, and 4 are accurate descriptions of redox processes: losing oxygen is reduction [2], gaining hydrogen is reduction [3], and gaining oxygen is oxidation [3]. Modern definitions also include electron transfer, where oxidation is the loss of electrons and reduction is the gain of electrons, often remembered by the mnemonic 'OIL RIG'.

Sources

1. [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
2. [3] 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. [2] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > What you have learnt > p. 14