A colourless crystalline salt X is soluble in dilute HCl . On adding NaOH solution, it gives a white precipitate which is insoluble in excess of NaOH .X is

Step-by-step solution

MgSO ₄ is soluble in HCl and gives MgCl ₂ and MgSO ₂ SO ₄(s)+2 HCl (a q) MgCl ₂+ H ₂ SO ₄(a q) On adding NaOH to MgCl ₂ , it gives white ppt. of Mg ( OH )₂ . MgCl ₂(a q)+ Excess 2 NaOH (a q) White ppt. Mg ( OH )₂(s)+ NaCl