Understanding Oxidation and Reduction Statements

This question asks to evaluate three statements concerning oxidation and reduction reactions.

Statement I Analysis

Statement I: A substance is said to be oxidised if it gains oxygen or loses hydrogen.

• This aligns with classical definitions of oxidation. Oxidation involves an increase in the oxidation state of an atom, which can occur through gaining oxygen atoms or losing hydrogen atoms.
• Conclusion: Statement I is correct.

Statement II Analysis

Statement II: A substance is reduced if it loses oxygen or gains hydrogen.

• This aligns with classical definitions of reduction. Reduction involves a decrease in the oxidation state, which can occur through losing oxygen atoms or gaining hydrogen atoms.
• Conclusion: Statement II is correct.

Statement III Analysis

Statement III: In every redox reaction, both oxidation and reduction occur simultaneously.

• The term "redox" is a combination of "reduction" and "oxidation." These processes are interdependent; one cannot happen without the other in a chemical reaction. If a substance is oxidized (loses electrons), another substance must be reduced (gains electrons).
• Conclusion: Statement III is correct.

Final Conclusion

Since all three statements (I, II, and III) accurately describe aspects of oxidation and reduction, the correct option includes all of them.

• Statement I is correct.
• Statement II is correct.
• Statement III is correct.

Therefore, the option stating I, II, and III are correct is the right choice.