A BaSO4 slurry is ingested just before the gastrointestinal tract is x-rayed because it is opaque to x-rays and defines the contours of the tract. Ba2+ ion is toxic, but the compound is nearly insoluble. If ?G° at 37°C (body temperature) is 59.1 kJ/mol for the process below.
BaSO4(s) reverse reaction arrow Ba2+(aq) + SO42-(aq)
What is [Ba2+] in the intestinal tract? (Assume that the only source of SO42- is the ingested slurry.)