Suppose you were given three unlabelled solutions. You know that one contains Iron (II) ions, another contains Iron (III) ions and the third has Silver ions, but you don’t know which is which. Devise a scheme by which you could identify each of the three cation solutions.

Question

Suppose you were given three unlabelled solutions.  You know that one contains Iron (II) ions, another contains Iron (III) ions and the third has Silver ions, but you don’t know which is which.  Devise a scheme by which you could identify each of the three cation solutions.

bobpursley · Answer

Color: Fe+2 solutions are pale green. Fe+3 are brown to yellowish brown, unless in acidic solutions. Silver solutions are colorless.

consider looking at color:
clear>Fe+3 in acid, or silver
so dip pH paper in, if it is not acid, it is silver. If it is clear, and acidic, Fe+3
pale green> Fe+2
brown, or brown/yellow> Fe+3

DrBob222 · Answer

If I answer this for you then I'm doing your thinking but this question is designed to make you think. Think about reactions that iron(II), iron(III) and Ag(I) undergo which give different results. Think about the color of some of the ppts. As an example, consider adding dilute HCl (or a solution of NaCl) to the three. What will happen that might identify one or more of the ions?