Can you please help me identify this unknown soloution?

Question

An unknown solution is tested as follows:

 

NaCl is added and no precipitate is formed

 

K2SO4 is added and no precipitate is formed.

 

Identify the unknown substance.

Answer 1

Impossible to identify the unknown from the limited information given.  Both tests that were performed were negative with respect to precipitate formation.  This tells you what the unknown IS NOT, but cannot tell you what it is.