Which one of the following is an oxidation-reduction reaction?
NaOH + HCl → NaCl + H₂O
CaO + H₂O → Ca(OH)₂
2Mg + O₂ → 2MgO
Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC NDA-2 – 2018
Let’s check the oxidation states of elements in each reaction:
A) NaOH + HCl → NaCl + H₂O: Na (+1→+1), O (-2→-2), H (+1→+1), Cl (-1→-1). No change in oxidation states. This is an acid-base neutralization reaction.
B) CaO + H₂O → Ca(OH)₂: Ca (+2→+2), O (-2→-2), H (+1→+1). No change in oxidation states. This is a combination reaction.
C) 2Mg + O₂ → 2MgO: Mg (0→+2), O (0→-2). Magnesium’s oxidation state increases from 0 to +2 (oxidation). Oxygen’s oxidation state decreases from 0 to -2 (reduction). This is a redox reaction.
D) Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl: Na (+1→+1), S (+6→+6), O (-2→-2), Ba (+2→+2), Cl (-1→-1). No change in oxidation states. This is a double displacement (precipitation) reaction.