[Amicus]

Hi I was wondering if anyone had any insights into the results of my experiment to identify an unknown acidic (salt) solution X reacted with a range of known solutions.
All reactions were carried out in test tubes and my results were concordant with the majority of the classes however we're all a bit mystified.

X mixed with Sodium hydroxide formed a white precipitate

X mixed with Sulphuric acid formed a white precipitate

X mixed with Potassium chromate (iv) formed a yellow very opaque precipitate
This solution then had HCL added which turned orange and see through

X mixed with acidified (with nitric acid) silver nitrate formed a white precipitate

X mixed with Sodium carbonate formed a white precipitate.   

I wondered if it might contain either Sulphuric acid or Hydrochloric acid due to the white ppt when mixed with silver nitrate, however, that doesn't seem to make sense with precipitate formed with sulphuric acid or Sodium carbonate... Is it likely that this is only one acid salt or might it be an impure sample? Any help suggestions or explanations would be very much appreciated.   

[Arkcon]

I wondered if it might contain either Sulphuric acid or Hydrochloric acid due to the white ppt when mixed with silver nitrate, however, that doesn't seem to make sense with precipitate formed with sulphuric acid or Sodium carbonate... Is it likely that this is only one acid salt or might it be an impure sample? Any help suggestions or explanations would be very much appreciated.   

I'm going to let you know that you're over thinking, at this point, and have gone in the wrong direction.  It is typical, in these sorts of tests, to add a slight amount of nitric or hydrochloric acids to the pre-test solution, to keep the ions in question soluble in storage.  Maybe that's why you noticed the solution is acid at the start.  But you test reagents you use should overwhelm the acid, and the observations you saw are what you should work with.