Can I get some help with this? both answers, please

Insoluble sulfide compounds are generally black in color. which of the following combinations could yield a black precipitate? check all that apply. na2s(aq)+kcl(aq) li2s(aq)+pb(no3)2(aq) pb(clo3)2(aq)+nano3(aq) agno3(aq)+kcl(aq) k2s(aq)+sn(no3)4(aq)

Why is the bottom layer of a trophic pyrimid the

If many scientists conduct the same or similar experiments, and all obtain similar results, a can be written, which is a generally agreed-upon statement that explains and predicts how a natural phenomenon works.