Which of the following chemical equations represents a redox reaction?

• A. CaCO_3 ightarrow CaO + CO_2
• B. H_2SO_4 + NaOH ightarrow Na_2SO_4 + 2H_2O
• C. 2Na + Cl_2 ightarrow 2NaCl
• D. AgNO_3 + NaCl ightarrow AgCl + NaNO_3

Answer: (C)

Verified step by step guidance

1. Identify what a redox reaction is: a chemical reaction involving the transfer of electrons, where one species is oxidized (loses electrons) and another is reduced (gains electrons).
2. Examine each given equation and determine if there is a change in oxidation states of any elements from reactants to products.
3. For the equation \(\mathrm{CaCO_3 \rightarrow CaO + CO_2}\), check the oxidation states of calcium, carbon, and oxygen to see if any change occurs.
4. For the equation \(\mathrm{H_2SO_4 + NaOH \rightarrow Na_2SO_4 + 2H_2O}\), analyze the oxidation states of hydrogen, sulfur, sodium, and oxygen to determine if electron transfer happens.
5. For the equation \(\mathrm{2Na + Cl_2 \rightarrow 2NaCl}\), observe that sodium goes from elemental form (oxidation state 0) to +1, and chlorine goes from 0 to -1, indicating a redox reaction involving electron transfer.