A solution contains some or all of the ions Cu2+, Al3+, K+, Ca2+, Ba2+, Pb2+, and NH4+. The following tests were performed, in order, on the solution. Addition of 6 M HCl produced no reaction.
Addition of H2S with 0.2 M HCl produced a black solid.
Addition of (NH4)2S produced a white solid.
Addition of (NH4)2HPO4 in NH3 produced no reaction.
The final supernatant when heated produced a purple flame.
Identify which of these ions were present in the solution, which were absent, and for which ones no conclusions can be drawn.

See explanation

Explanation:

If we look at the tests to be performed on the compounds carefully, we will notice that;

i) Addition of H2S with 0.2 M HCl produced a black solid. This black solid may result from the reaction;

H2S + Cu2+ >CuS(balck solid) + H2

or

H2S + Pb2+  >PbS(balck solid) + H2

Hence, Cu2+ or Pb2+  may be present

ii) Addition of (NH4)2S produced a white solid. This means that  K^+ may be present because the white precipitate is formed during metathesis.

iii) Potassium ion is known to burn with a purple flame.

Hence the suspected ions are;

Cu2+ , Pb2+ and  K^+

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