Which solution will turn red litmus paper blue? NH₄Cl(aq) NaCl(aq) Na₃PO₄(aq) HCl(aq) Show answer 📝 Detailed explanation Na₃PO₄ is a salt of a strong base (NaOH) and a weak acid (H₃PO₄). The phosphate ion hydrolyzes to produce OH⁻, making the solution basic, which turns red litmus blue.