FA4 contains two cations, zinc ion and chromium(III) ion.
The identities of the cations are unknown to Student A. However, Student A is aware of the presence of two cations.
Student A was told to conduct a series of tests below:
1. To 1 cm depth of the test solution, add NH3(aq) dropwise until no further change is seen.
3. To the filtrate, add dilute nitric acid dropwise until in excess.
Student A recorded the observations as follow:
1. Pale green ppt formed, insoluble in excess.
3. White ppt reformed, soluble in excess.
For the following questions, select the correct option to amend the observations above.