[Xhevin]

I have a test tomorrow and I can't seem to solve a fairly easy exercise. Please can somebody help me with the electrolyse of Ag2S with H2O ( concentrated) It would be much appreciated!!

[Borek]

Nothing of what you wrote makes sense, please elaborate.

Please remember you have to show your attempts at solving the problem to receive help, this is a forum policy.

[INeedSerotonin]

Does Ag2S dissociate in water? How?

Which ion will go to the cathode? Which ion will go to the anode? Which ion is attracted to the positive pole? Which ion is attracted to the negative pole?

Which compound will be formed? Which compound will remain in the electrolytic tank?

Would S^2- become rhombic, orthorhombic or perhaps another allotrope?

(Here I am trying to help; but I myself don't know the answer. Somebody please shed some light.)

[AWK]

First of all check solubility of Ag₂S in water. Then think about the hydrolysis of sulfide anion.
From this information and the oxidation and reduction potentials, it can be concluded that electrolysis is theoretically possible, but it requires eternity to carry it out.

Would S^2- become rhombic, orthorhombic or perhaps another allotrope?

Allotropy concerns elements!
In elemental sulfur, all roads lead to its orthorhombic S₈ allotropic form. The monoclinic sulfur can be obtained only at temperatures between ~ 95 and 120 C. When cooling monoclinic sulfur, transparent needle crystals become opaque in a few minutes, and while maintaining the monoclinic sulfur needle form we obtain orthorhombic sulfur inside.

[INeedSerotonin]

Thank you! Does it mean that Ag⁺ will gain one electron and become metallic Ag, and 8 moles of ion sulphur will lose two electrons and become orthorrombic in electrolysis?

[AWK]

Yes (theoretically) and no (practically). The solubility of Ag₂S in water is  of ~10^-15 M. OH^- ion concentration in pure water is  of ~10^-7 M. At this concentration of sulfide ion it will almost completely hydrolyze to H₂S and trace amounts of HS^- ions (note - trace in relation to the concentration of 10^-15 M). In this case, the voltage could be adjusted so that the water will not undergo electrolysis. But the extremely low current caused by the ionic conductivity of water will be even thousands of times greater than that used for the electrolytic decomposition of AgOH and AgHS. Rather, certainly no one tried to obtain metallic silver by this method, but e.g. by the electrolysis of molten Sb₂S₃, the elemental Sb is obtained.

Does it mean that Ag+ will gain one electron and become metallic Ag, and 8 moles of ion sulphur will lose two electrons...

One Ag⁺ ion corresponds to 1/2 sulfur atom, and this corresponds to 1/16 of the S₈ molecule.