CuS precipitates dissolve in hot HNO3. The hot HNO3 oxidizes the sulfide ion in the precipitates to free elemental sulfur, forming NO(g) as its reduction product. For CuS, 3CuS(s) + 8H(aq) + 2NO3(aq) = 3Cu(aq) + 2NO(g) + 3S(s) + 4H2O(l) I have a few questions here. Why is HNO3 split up on the reactants side? Does it matter what the coefficient is of CuS? if so, how do know whether it 3 or 4 or 2?