Answer:
a. Na₂S and (NH₄)₃PO₄ .
Step-by-step explanation:
To know which salts are soluble we need to remember some solubility rules. And apply these as follows:
* All compounds of group 1 (Li⁺, Na⁺, K⁺, etc.) are soluble, Na₂S is soluble.
* All ammonium salts are soluble,
(NH₄)₃PO₄ is soluble.
* All Cl⁻, I⁻, Br⁻ are soluble except when are with Ag⁺, Hg₂²⁺, Pb²⁺, Hg₂Cl₂ is insoluble
* Carbonates are insoluble except those with group 1 or ammonium, CdCO₃ is insoluble
* All sulfates are soluble except those with Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Ag⁺. PbSO₄ is insoluble.
Right solution is:
a. Na₂S and (NH₄)₃PO₄