Q.$[\text{Co}(\text{NH}_3)_5\text{Br}]\text{SO}_4$ and $[\text{Co}(\text{NH}_3)_5\text{SO}_4]\text{Br}$ have the same overall composition but are distinct compounds. Name the type of isomerism they show, and describe a simple chemical test that would distinguish between them.

[!TLDR] Ionization isomerism: SO$_4^{2-}$/Br$^-$ swap between coordinated and free counter-ion roles. [!ANSWER] Ionization isomerism; test with BaCl$_2$ (white BaSO$_4$ ppt on …

$[\text{Co}(\text{NH}_3)_5\text{Br}]\text{SO}_4$ and $[\text{Co}(\text{NH}_3)_5\text{SO}_4]\text{Br}$ have identical overall composition (one Co, five $\text{NH}_3$, one Br, one $\text{SO}_4$) but differ in which of $\text{Br}^-$ and $\text{SO}_4^{2-}$ is directly coordinated to cobalt (inside the coordination sphere) versus which is a free counter ion outside it — this is ionization isomerism, since the two compounds ionize differently in solution, giving different free ions. In the first compound, $\text{Br}^-$ is coordinated and $\text{SO}_4^{2-}$ is free; its solution therefore gives an immediate white precipitate of $\text{BaSO}_4$ on adding $\text{BaCl}_2$ solution (the standard test for free sulfate ion), but does NOT immediately precipitate $\text{AgBr}$ with $\text{AgNO}_3$, since the coordinated bromide is not free to react. In the second compound, $\text{SO}_4^{2-}$ is coordinated and $\text{Br}^-$ is free; its solution gives an immediate pale yellow precipitate of $\text{AgBr}$ on adding $\text{AgNO}_3$ (the standard test for free bromide ion), but does NOT immediately precipitate $\text{BaSO}_4$ with $\text{BaCl}_2$. Testing a solution of the unknown compound with either reagent and o …

Recognize that the two compounds have the same overall formula but different groups inside versus outside the coordination sphere — this is ionization isomerism; distinguish them using a prec …

Confusing ionization isomerism with linkage isomerism — here, two DIFFERENT ligand/counter-ion species (Br$^-$ and SO$_4^{2-}$) swap roles, rath …