Question

which is evidence that the single replacement reaction shown below is also a redox reaction? cu + 2agno₃ → cu(no₃)₂ + 2ag
the reaction involves the element oxygen.
there are four different elements in the reaction.
silver is in a compound as a reactant, but is a pure element as a product.
the nitrate ion, no₃⁻, does not split apart during the reaction.

Explanation:

Redox reactions involve a change in oxidation state. In the given reaction, silver changes from an ionic state in the reactant ($AgNO_3$) to a neutral elemental state in the product ($Ag$), indicating a transfer of electrons and thus a redox reaction.

Answer:

Silver is in a compound as a reactant, but is a pure element as a product.