Insoluble sulfide compounds are generally black in color.
which of the following combinations could yield a black precipitate?
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

A black precipitate is formed by the reaction; Li2S(aq) + Pb(NO3)2(aq) > PbS(s) + 2LiNO3(aq) and K2S(aq) + Sn(NO₃)₄(aq)→ SnS(s) + KNO₃(aq)

A double decomposition reaction is a type of reaction in which the cations exchange anion partners in the product. Sometimes, a double decomposition reaction yields a precipitate. A precipitate is a solid product of the reaction between two aqueous species.

Given the options in the question, a black precipitate is formed by the reaction; Li2S(aq) + Pb(NO3)2(aq) > PbS(s) + 2LiNO3(aq) and K2S(aq) + Sn(NO₃)₄(aq)→ SnS(s) + KNO₃(aq)

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Li₂S(aq)+Pb(NO₃)₂(aq) → PbS(s) + LiNO₃(aq)

K2S(aq)+Sn(NO₃)₄(aq→ SnS(s) + KNO₃(aq)

In our case; In the equations given, some reactions will take place to form a precipitate while others will not occur.

That is;

The first reaction will not occur.

The second equation is a precipitation reaction that forms lead(ii)sulfide which is a black precipitate.

The third reaction will not take place.

The fourth reaction will be a precipitation reaction forming silver chloride precipitate.

The fifth equation is also a precipitation reaction that forms tin(ii) sulfide, SnS which is a black precipitate.

Therefore; the equations that answers our question are;

- lead + phosphoric acid = hydrogen + lead(ii) phosphate

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