Barium sulphate can be made by mixing solutions containing the barium and sulphate ions. The ionic reaction is: Ba(2+)(aq) +SO4(2-)(aq) -> BaSO4(s)
Barium ions are toxic but barium sulphate is safe to consume
a) Which ion is limiting and which is excess reagent when barium sulphate is made? Justify the predicion.
b) Why is it important to prepare the barium sulphate mixture as accurately as possible?
When Ba(2+) ions react with SO4(2-) ions BaSO4 is precipitated. Barium ions are toxic in nature but barium sulfate does not pose any health risk.
During the chemical reaction: Ba(2+)(aq) +SO4(2-)(aq) -> BaSO4(s) it is essential for all the Ba2+ ions to be consumed so that the toxic reactants are eliminated. As SO4(2-) is not toxic even if SO4(2-) ions are present in the reactants when the reaction is complete it does not pose a health risk.
Therefore in this reaction Ba(2+) is the limiting reagent. During the production of BaSO4 it would be ensured that all of the Ba(2+) is consumed. Even if each Ba(2+) ion does not react with a SO4(2-) ion adding a sufficiently large number of SO4(2-) ions would ensure that all the Ba(2+) is converted to BaSO4.
It is important to prepare the Ba(2+) and SO4(2-) mixture as accurately as possible to ensure all the Ba(2+) is consumed as well as minimize wastage of the SO4(2-) ions.