Question

Which aqueous solution should form a precipitate with aqueous cu(no3)2? 1. kno3 2. cuso4 3. k2so4 4. k2s?

Answer 1

Reaction of Cu(NO₃)₂ with each salt is as follow, 

1) with KNO₃;

                  Cu(NO₃)₂  +  KNO₃   →   Cu(NO₃)₂  +  KNO₃

Both salt products are water soluble.

2) With CuSO₄;

                  Cu(NO₃)₂  +  CuSO₄   →   CuSO₄  +  Cu(NO₃)₂
Again both Salt products are water soluble.

3) With K₂SO₄;

                  Cu(NO₃)₂  +  K₂SO₄   →  CuSO₄  +  2 KNO₃
Again both salt products are water soluble.

4) With K₂S;

                  Cu(NO₃)₂  +  K₂S   →   CuS  +  2 KNO₃
In this case CuS is water insoluble, hence precipitates out.

Result:
           Option-4 is the correct answer.