Question

The barium ion is toxic to humans. However, barium sulfate is commonly used as an image enhancer for gastrointestinal x-rays. What does this imply about the position of the equilibrium shown below?
$BaS{O_4} \to B{a^{ + 2}} + S{O_4}^{ - 2}$

Answer 1

We are already provided with the information that barium ion is toxic in nature and also, we are given the equation. This could be explained with an example. According, to the toxic dosage, we shall calculate the mass of barium. Then, according to the solubility product, we shall find the concentration of barium per litre in barium sulphate and thus, the volume of barium sulphate solution required to be harmful to humans.

Complete step-by-step answer: We already know that barium sulfate is highly insoluble in water.
So, we consider a practical example:
The dose of barium ion must be about $200{\text{ mg/}}\left( {{\text{kg}}{\text{.day}}} \right)$ to see adverse effects.
For a 50 kg individual, this corresponds to $10{\text{ g/day}}$ of barium.
$BaS{O_4} \to B{a^{ + 2}} + S{O_4}^{ - 2}$
${K_{sp}} = 1.1 \times {10^{ - 10}}$
This corresponds to a molar concentration of ${\text{1}}{{.0 \times 1}}{{\text{0}}^{{\text{ - 5}}}}{\text{mol/L B}}{{\text{a}}^{{\text{ + 2}}}}{\text{ or 1}}{\text{.4 mg Ba/L}}$.
An individual would have to ingest about 7000 L of saturated $BaS{O_4}$ solution to reach this level.
Few individuals have stomachs that are resilient enough to hold this volume.
Thus, it is quite safe to ingest barium sulfate for gastrointestinal X-rays.

Additional Information: We should know that although soluble salts of barium are moderately toxic to humans, barium sulfate is nontoxic due to its insolubility. The most common means of inadvertent barium poisoning arises from the consumption of soluble barium salts mislabeled as $BaS{O_4}$ . So, the reason that there is such a profound difference in toxicity between two salts, which on the surface look more or less the same, the insolubility of barium sulfate is why it is so safe to use and barium chloride can kill you. As mundane, pink, or beautiful as bismuth can be, it can also be rather toxic.

Note: Thus, we can conclude that although barium carbonate is relatively insoluble in water, it is toxic to humans because it is soluble in the gastrointestinal tract. The insoluble compounds of barium (notably sulfate) are inefficient sources of barium ion and are therefore generally nontoxic to humans.