Diagramming Voltaic Cells
Since the Cr electrode is negative, the half-reaction releases electrons:
Cr(s) Cr3+(aq) + 3 e- [oxidation; anode]
Writing the balanced overall cell reaction. We triple the reduction
half-reaction to balance electrons, and combine the half-reactions to
obtain the overall spontaneous reaction:
Cr(s) + 3 Ag+(aq) Cr3+(aq) + 3 Ag(s)
Cr(s) Cr3+(aq) Ag+(aq) Ag(s)
Determining direction of electron and ion flow. The released e- in the Cr
electrode (negative) flow through the external circuit to the Ag electrode
(positive). As Cr3+ ions enter the anode electrolyte, NO3- ions enter from
the salt bridge to maintain neutrality. As Ag+ ions leave the cathode
electrolyte and plate out on the Ag electrode, K+ ions enter from the salt
bridge to maintain neutrality.
| Previous slide | Next slide | Back to first slide | View graphic version |