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Calculate the molar solubility of Hg 2 Cl 2 .
Determine the direction of change. Before any Hg 2 Cl 2 dissolves, Q is zero, and the reaction will shift to the right to reach equilibrium.
Determine x and equilibrium concentrations. Concentrations and changes are given in the following ICE table:
Note that the change in the concentration of Cl – (2 x ) is twice as large as the change in the concentration of ( x ) because 2 mol of Cl – forms for each 1 mol of that forms. Hg 2 Cl 2 is a pure solid, so it does not appear in the calculation.
Solve for x and the equilibrium concentrations. We substitute the equilibrium concentrations into the expression for K sp and calculate the value of x :
The molar solubility of Hg 2 Cl 2 is equal to or 6.5 10 –7 M .
Check the work. At equilibrium, Q = K sp :
The calculations check.
1.2 10 –3 M
Tabulated K sp values can also be compared to reaction quotients calculated from experimental data to tell whether a solid will precipitate in a reaction under specific conditions: Q equals K sp at equilibrium; if Q is less than K sp , the solid will dissolve until Q equals K sp ; if Q is greater than K sp , precipitation will occur at a given temperature until Q equals K sp .
Various types of medical imaging techniques are used to aid diagnoses of illnesses in a noninvasive manner. One such technique utilizes the ingestion of a barium compound before taking an X-ray image. A suspension of barium sulfate, a chalky powder, is ingested by the patient. Since the K sp of barium sulfate is 1.1 10 –10 , very little of it dissolves as it coats the lining of the patient’s intestinal tract. Barium-coated areas of the digestive tract then appear on an X-ray as white, allowing for greater visual detail than a traditional X-ray ( [link] ).
Further diagnostic testing can be done using barium sulfate and fluoroscopy. In fluoroscopy, a continuous X-ray is passed through the body so the doctor can monitor, on a TV or computer screen, the barium sulfate’s movement as it passes through the digestive tract. Medical imaging using barium sulfate can be used to diagnose acid reflux disease, Crohn’s disease, and ulcers in addition to other conditions.
Visit this website for more information on how barium is used in medical diagnoses and which conditions it is used to diagnose.
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