Part A. Barium sulfate, BaSO4, is used in medical imaging of the gastrointestina

Question

Part A. Barium sulfate, BaSO4, is used in medical imaging of the gastrointestinal tract because it is opaque to X rays. A barium sulfate solution, sometimes called a cocktail, is ingested by the patient, whose stomach and intestines can then be visualized via X-ray imaging. If a patient ingests 240mL of a saturated barium sulfate solution, how much toxic Ba2+ ion has the patient consumed?

The solubility product Ksp of BaSO4 is 1.110?10.

Part B. There are some data that suggest that zinc lozenges can significantly shorten the duration of a cold. If the solubility of zinc acetate, Zn(CH3COO)2, is 43.0 g/L, what is the solubility product Ksp of this compound?

Explanation / Answer

Part A

BaSO4 -------------> Ba2+ + SO42-

Ksp = [Ba2+] [SO42-] = 1.1 x 10^-10

As [Ba2+] and [SO42-] will be same ( as same stoichiometry)

[Ba2+] = square root (1.1 x 10^-10) =1.05 x 10^-5 M

Now, moles of Ba2+ present = molarity x volume in Litre = 1.05 x 10^-5M x 0.240 L =2.52 x 10^-6

mass of Ba2+ = no. of moles x molar mass= 2.52 x 10^-6 mol x 137.327 g/mol = 3.46 x 10^-4 g

Part B

Zn(CH3COO)2--------------> Zn2+ + 2CH3COO-

moles of Zn(CH3COO)2 = 43.0 g / 183.48 g/mol = 0.234 mol

concentration of Zn2+ = no. of moles/ volume in litre = 0.234 mol / 1L = 0.234 M

concentration CH3COO- = 2 x 0.234 = 0.468 M (as 2 times acetate ions are produced)

Ksp = [Zn2+] [CH3COO-]^2 = 0.234 x (0.468)^2 =5.13 x 10^-2

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