JEE Advanced Chemistry: Analytical Chemistry questions with solutions

Q1. Which of the following anions does NOT produce a precipitate with BaCl2 solution but DOES give a precipitate with AgNO3 solution?

1. CO3²- (aq.)
2. C2O4²- (aq.)
3. NO3- (aq.)
4. S²- (aq.)

Answer: S²- (aq.)

S²- satisfies both conditions: it does not give a precipitate with BaCl2 (BaS is soluble enough to not precipitate distinctly) but gives a black insoluble precipitate of Ag2S with AgNO3. NO3- gives no precipitate with either reagent.