After being given an unknown, you perform the following tests to determine the identity

After being given an unknown, you perform the following tests to determine the identity of the cations in solution:

- The addition of NaOH produces a vapor.

- The addition of HCl produces a white precipitate

- The addition of buffered NH4+/NH3 does not produce a precipitate.

- A flame test produced no color

- The addition of ammonium oxalate produced no precipitate

- The addition of strong base produces a precipitate

- After adding a strong base, the resulting solution does not react with a solution of K4Fe(CN)6

Below is the list of the ten ions we studied for the qualitative analysis experiment:

Na+, NH4+, Ag+, Fe3+, Al3+, Cr3+, Ca2+, Mg2+, Ni2+, Zn2+