Question

For an investigation, a student poured a blue solution of CuSO4 into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes. The student inferred that a chemical reaction occurred. What evidence supports this inference?

A) The CuSO4 solution turned blue when the zinc metal was added.
B) None of these
C) A dark solid formed on the zinc metal.
D) The zinc metal remained silver-colored and shiny.

Answer 1

The formation of a dark solid on the zinc strip is evidence of a redox reaction between zinc and the blue CuSO4 solution, resulting in the reduction of copper ions to solid copper and oxidation of zinc to ions.

Step-by-step explanation:

The evidence that supports the inference that a chemical reaction occurred when a shiny, silver-colored strip of zinc metal was placed in a blue solution of CuSO4 is C) A dark solid formed on the zinc metal. This dark solid is elemental copper that has formed as a result of a direct redox reaction between the zinc metal and the copper ions in the solution. The zinc strip begins to darken and appears less shiny as zinc is oxidized to Zn2+ ions, which dissolve into the solution. Simultaneously, the Cu2+ ions in the blue CuSO4 solution are reduced to solid copper. As a result, the solution will eventually lose its blue color because the concentration of Cu2+ ions decreases. This direct transfer of electrons from the zinc metal to the aqueous copper(II) ions is spontaneous and a characteristic of a redox reaction.