Solubility of Group 2 metal sulfates in water

Steps:

• Apply solubility rules: Group 2 chlorides soluble; carbonates insoluble; hydroxides slightly to moderately soluble (Mg least); sulfates generally soluble (decreasing down group).
• Examine option A: BaCl₂ soluble, but CaCO₃ and Mg(OH)₂ insoluble.
• Examine option B: Ba(OH)₂ and Ca(OH)₂ soluble/slightly soluble, but SrCO₃ insoluble.
• Confirm option C: BaSO₄, CaSO₄, MgSO₄ all Group 2 sulfates, soluble per rules.
• Examine option D: CaSO₄ soluble, but BaSO₄ and Mg(OH)₂ insoluble.

Why C is correct:

• Group 2 sulfates (MSO₄, M = Mg, Ca, Ba) are classified as soluble in water under standard qualitative analysis rules, despite decreasing solubility trend.

Why the others are wrong:

• A: Contains insoluble CaCO₃ and Mg(OH)₂.
• B: Contains insoluble SrCO₃.
• D: Contains insoluble BaSO₄ and Mg(OH)₂.

Final answer: C