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.