BSc Nursing GNM 2019 Solved Paper

As we know, solubility product is directly proportional to concentration of solute particles. If concentration of solute particle is more, it will precipitate first.
Also, when H2S gas is passed through a solution containing the ions, more H+ions will be furnished and hence, due to common ion effect, The concentration also increases. Since, NiS has greater value of solubility product, hence it will precipitate first.