Question: Michael Faraday was a consummate experimentalist. In his earliest studies of electrolysis, he used the volume of gas evolved by the decomposition of water as a measure of the amount of electricity (total charge) passing through his electrolysis cells. Figure illustrates an experiment to study the electrolysis of tin chloride (SnCl2). Two platinum electrodes are immersed in a molten bath of SnCl2 and connected in series with a second cell containing a weak solution of sulfuric acid in water. (Because the cells are connected in series, the same current flows through each cell.) In the reaction, gaseous Cl2 is evolved at one electrode, and solid (metallic) Sn is plated onto the second electrode. Faraday measured the mass of the Sn and the volumes of the H2 and O2 evolved in the water cell.
Faraday stopped the experiment when the total volume of H2 and O2 equaled 63.1 cm3, and found that 0.207 gm of Sn had been deposited.
a. What volume of H2 was evolved? Assuming standard temperature and pressure, what fraction of a mole is this? (The overall reaction is 2H2O → 2H2 + O2.)
b. What reactions are occurring at the two electrodes in the SnCl2 cell? What fraction of a mole of Sn is deposited?
c. From Faraday's numbers, find the atomic weight of Sn.
d. If the Cl2 gas had been collected, what would its volume have been?
Fig. - An arrangement for studyimg the electrolysis of SnCl2.