Question

A solution contains 0.1 M Sr2+ ions and 0.1 M Ag+ ions. Addition of an equal volume of a 0.5 M solution of which reagent will cause precipitation of a strontium salt but not a silver salt?

(A) NaNO3
(B) NaF (C) NaOH (D) NaCl

Answer 1

Adding an equal volume of a 0.5 M solution of NaF will cause precipitation of a strontium salt but not a silver salt in the given solution.

Step-by-step explanation:

When equal volumes of a 0.1 M solution of Sr2+ ions and a 0.1 M solution of Ag+ ions are mixed, both strontium and silver salts can potentially precipitate out of solution depending on the reagent added. To determine which reagent will cause precipitation of a strontium salt but not a silver salt, we can look at the solubility rules.

According to the solubility rules, most nitrate (NO3-) salts are soluble, so adding NaNO3 (A) to the solution will not result in precipitation of either strontium or silver salts. Similarly, most chloride (Cl-) salts are also soluble, so adding NaCl (D) to the solution will not cause precipitation of strontium or silver salts.

However, when an equal volume of a 0.5 M solution of NaF (B) is added, the fluoride ions combine with the strontium ions to form an insoluble strontium fluoride (SrF2) precipitate, while the silver ions remain in solution as the soluble silver fluoride (AgF). Therefore, the addition of NaF will cause precipitation of a strontium salt but not a silver salt.

Thus, the correct reagent is NaF (B).