What is observed when concentrated hydrochloric acid is added to an aqueous solution of cobalt(II) sulfate, CoSO4\text{CoSO}_4CoSO4, until no further change occurs?
A colourless gas is evolved and a precipitate forms.
A colourless gas is evolved and no precipitate forms.
A precipitate forms that dissolves in an excess of concentrated hydrochloric acid.
The solution changes colour and no precipitate forms.