70
2 – Methods and techniques
Three separable α-AgI pellets are inserted between a silver anode and a platinum
cathode. To measure the current, a silver coulometer is inserted in the circuit.
The electrolyte of the coulometer consists of a solution of silver nitrate. The
circuit carries a current of 100 mA for 1 h. The analysis of the results of this
experiment leads to the following conclusions:
2 no change is detected in the mass of tablets A and B,
2 the mass of the silver anode decreases by Δm, which equals the mass deposited in the coulometer,
2 the mass of tablet C remains constant,
2 the mass of the platinum cathode increased by Δm.
1. What conclusions about the mode of conduction in α-AgI can we draw from
this experiment?
2. Deduce the value of Δm.
Data
M Ag = 107.9 g mol
−1
  M I = 126.9 g mol
−1