Can you help me with this problem about salts?

Question

Consider five unlabled bottles of the following salts: AgCl, BaCl2, NaCl, CoCl2, and HCl. Identify the compound that can be distinguished by adding 1.0 M Na2SO4 to each of the samples. Please explain your answer. 

Answer 1

2AgCl + Na2SO4 ==> 2NaCl(aq) + Ag2SO4(s)  white ppt - Also note that AgCl is insoluble

BaCl2 + Na2SO4 ==> BaSO4(s) + 2NaCl(aq) white ppt - Also note that BaCl2 is insoluble

NaCl + Na2SO4 ==> no reaction

CoCl2 + Na2SO4 ==> CoSO4(s) + 2NaCl white ppt formed - CoCl2 is soluble but will form a ppt.

HCl + Na2SO4 ==> no reaction but pH will be acidic

 

So, the only ones that can be distinguished are NaCl and HCl and these can be distinguished by pH.  The NaCl solution will have a neutral pH, the HCl solution will be pH ,7.  All others will form a precipitate as their