What precipitate will form when determining sulfate anion in natural water by gravimetric method?

The formation of BaSO4, or barium sulfate, as a precipitate when determining sulfate anions in water using the gravimetric method is due to the reaction between barium ions (Ba²⁺) and sulfate ions (SO4²⁻). In gravimetric analysis, the goal is to isolate and weigh a precipitate that can be used to quantify the concentration of a specific ion.

When barium chloride (BaCl2) or barium nitrate (Ba(NO3)2) is added to a sample containing sulfate ions, a double displacement reaction occurs. The barium ions react with sulfate ions to form a solid precipitate of barium sulfate, which is known for its low solubility in water. This precipitate can then be filtered, washed, dried, and weighed to measure the amount of sulfate in the sample.

Barium sulfate has several desirable characteristics for this analysis: it has a well-defined stoichiometry, its precipitation can be controlled by adjusting the concentrations, and it is stable and pure when properly handled. The measured mass of the barium sulfate can be converted back to determine the concentration of sulfate in the original sample using stoichiometric calculations.

The other options, such as BaO