Question

How is sulfate ion reduced to sulfide ion?

Answer 1

Do you mean `"sulfate to sulfide............?"`

Explanation:

Well, this is a formal reduction:

`"sulfate(+VI) undergoes 8 electron to S(-II)":`

`SO_4^(2-) + 8H^+ + 8e^(-) rarr S^(2-) + 4H_2O(l)`

I am no biochemist, but I believe this is achieved by bacterial action. Are charge and mass balanced?