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? BaSO4 Ba+2 + SO4-2?

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Answer 1 · 2016-12-27T02:08:10

It implies that the position of equilibrium lies far to the left.

The dose of barium ion must be about 200 mg/(kg·day) to see adverse effects.

For a 50 kg individual, this corresponds to 10 g/day of barium.

Barium sulfate is highly insoluble in water.

$"BaSO"_4"(s)" ⇌ "Ba"^"2+""(aq)" + "SO"_4^"2-""(aq)"$

$K_"sp" = 1.1 × 10^"-10"$

This corresponds to a molar concentration of $1.0 × 10^"-5"color(white)(l) "mol/L Ba"^"2+"$ or $"1.4 mg Ba/L"$ .

An individual would have to ingest about 7000 L of saturated $"BaSO"_4$ 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.