Answer:
Na2S, (NH4)3PO4
Explanation:
We can decide what compounds are soluble by considering the solubility rules that apply.
CdCO3 is not soluble in water because all carbonates are insoluble except those of ammonium, sodium and potassium.
Na2S is soluble in water because all sulphides are insoluble except those of sodium, potassium and ammonium.
PbSO4 is insoluble in water because all sulphates are soluble except those of lead and barium. The sulphate of calcium is only slightly soluble in water.
(NH4)3PO4 is soluble in water because all phosphates are insoluble except those of sodium, potassium and ammonium.
Hg2Cl2 is insoluble in water because all chlorides are soluble except those of lead, mercury II and silver.
