Final answer:
Of the listed reactions, only B.Cu + 2AgNO₃ -> Cu(NO₃)2 + 2Ag is a redox reaction where copper is oxidized and silver is reduced, indicating a transfer of electrons.
Step-by-step explanation:
The question presented asks which of the following are oxidation-reduction reactions: A.PCl₃ + Cl₂ -> PCl₅ B.Cu + 2AgNO₃ -> Cu(NO₃)₂ + 2Ag C.CO₂ + 2LiOH -> Li₂CO₃ + H₂O D.FeCl₂ + 2NaOH -> Fe(OH)₂ + 2NaCl. Oxidation-reduction reactions, also known as redox reactions, involve the transfer of electrons between reactants, resulting in a change in oxidation states.
Answer A (PCl₃ + Cl₂ -> PCl₅) is not a redox reaction as there is no change in oxidation state. Phosphorus starts as P(+3) and stays P(+3), while chlorine starts and remains Cl(0) and Cl(-1).
Answer B (Cu + 2AgNO₃ -> Cu(NO₃)₂ + 2Ag) is a redox reaction. Copper (Cu) is oxidized, going from an oxidation state of 0 to +2, and silver (Ag+) is reduced, going from an oxidation state of +1 to 0.
Answer C (CO₂ + 2LiOH -> Li₂CO₃ + H₂O) is not a redox reaction because there is no electron transfer between different atom types; carbon remains at an oxidation state of +4 and oxygen at -2.
Answer D (FeCl₂ + 2NaOH -> Fe(OH)₂ + 2NaCl) is not a redox reaction either, as iron maintains its +2 oxidation state, and there is no change in the oxidation state of chlorine or oxygen.