I have found a balanced redox equation for removal of silver sulfide using sodium hydrogen carbonate in aluminium to say:

Question

2Al + 3Ag2S + 6H2O --> 6Ag + 2Al2(OH)3 + 3H2S

What happens to the Na and C component of the sodium hydrogen carbonate? And why is it not included on LHS of equation?

Answer 1

The Al and Ag2S (with water) is an electrolytic cell but it needs something ionic to conduct the electrons between the Ag^+ of Ag2S and Al metal. NaHCO3 does that job. In fact, ANYTHING ionic will work. But the ionic compound doesn't enter into the reaction, other than the conducting of electrons from one electrode to the other, and it isn't included in the redox equation.

Answer 2

Thank you!!