In a voltaic cell, the spontaneous reaction that occurs is Cr (s) + Cu²⁺→Cu (s) + Cr²⁺. Consider the following three statements and choose the correct answer.
I. The chromium metal is the negative electrode.
II. A salt bridge is unnecessary in this voltaic cell.
III. Copper (II) ions are reduced.

Question

Quizplus · Accepted Answer

I. The direction of electron flow in an electrochemical cell is always from the anode (negative electrode) to the cathode (positive electrode). In this reaction, chromium metal is oxidized and loses electrons, so it is the anode and is indeed the negative electrode.

II. A salt bridge is necessary to maintain charge neutrality in the two half-cells. In this cell, the copper ions from the copper(II) sulfate solution are reduced at the cathode, creating a buildup of positive charge as the solution loses copper ions. The salt bridge allows for the flow of negative ions to move from the salt bridge to the copper(II) sulfate solution to balance the charge. Therefore, statement II is false.

III. Copper(II) ions are indeed reduced in this reaction. The Cu(II) ions in solution are reduced to Cu metal at the cathode. Therefore, statement III is true.

Putting all three statements together, we can see that the correct choice is D.

In a Voltaic Cell, the Spontaneous Reaction That Occurs Is