An industrial wastewater sample contains equal concentrations of dissolved magnesium ions, Mg2+(aq)\text{Mg}^{2+}(aq)Mg2+(aq), and highly toxic barium ions, Ba2+(aq)\text{Ba}^{2+}(aq)Ba2+(aq). An environmental chemist wants to remove the toxic barium ions from the wastewater by selective precipitation, leaving the non-toxic magnesium ions dissolved in the solution.
Which of the following reagents should be added to the wastewater sample to achieve this?
Sodium hydroxide, NaOH(aq)\text{NaOH}(aq)NaOH(aq)
Sodium sulfate, Na2SO4(aq)\text{Na}_2\text{SO}_4(aq)Na2SO4(aq)
Sodium carbonate, Na2CO3(aq)\text{Na}_2\text{CO}_3(aq)Na2CO3(aq)
Nitric acid, HNO3(aq)\text{HNO}_3(aq)HNO3(aq)
