Describing a Voltaic CellThe oxidation–reduction

Chapter , Problem 1PE

(choose chapter or problem)

Problem 1PE

Describing a Voltaic Cell

The oxidation–reduction reaction

Cr2O7 2–(aq) + 14 H+(aq) + 6 I-(aq) → 2 Cr3+(aq) + 3 I2(s) + 7 H2O(l)

is spontaneous. A solution containing K2Cr2O7 and H2SO4 is poured into one beaker, and a solution of KI is poured into another. A salt bridge is used to join the beakers. A metallic conductor that will not react with either solution (such as platinum foil) is suspended in each solution, and the two conductors are connected with wires through a voltmeter or some other device to detect an electric current. The resultant voltaic cell generates an electric current. Indicate the reaction occurring at the anode, the reaction at the cathode, the direction of electron migration, the direction of ion migration, and the signs of the electrodes.

The following two half-reactions occur in a voltaic cell:

Ni(s) → Ni2+(aq) + 2 e– (electrode = Ni), Cu2+(aq) + 2 e–→ Cu(s) (electrode = Cu)

Which one of the following descriptions most accurately describes what is occurring in the half-cell containing the Cu electrode and Cu2+(aq) solution?

(a) The electrode is losing mass and cations from the salt bridge are flowing into the half-cell., (b) The electrode is gaining mass and cations from the salt bridge are flowing into the half-cell., (c) The electrode is losing mass and anions from the salt bridge are flowing into the half-cell., (d) The electrode is gaining mass and anions from the salt bridge are flowing into the half-cell.