Multiple Choice
Which of the following best determines whether a molecule is soluble or insoluble in water?
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6. Chemical Quantities & Aqueous Reactions
Solubility Rules
Multiple Choice
Which of the following ions is most likely to form an insoluble sulfate compound?
A
Ba^{2+}
B
K^{+}
C
Na^{+}
D
Ca^{2+}
Verified step by step guidance1
Recall the general solubility rules for sulfates (SO_4^{2-}): most sulfate salts are soluble in water, but there are notable exceptions involving certain metal ions.
Identify the ions given: K^{+}, Na^{+}, Ca^{2+}, and Ba^{2+}. Both K^{+} and Na^{+} are alkali metal ions, which typically form soluble sulfate salts.
Recognize that Ca^{2+} and Ba^{2+} are alkaline earth metal ions. Among these, CaSO_4 is slightly soluble, while BaSO_4 is known to be highly insoluble in water.
Use the solubility trend for sulfates of alkaline earth metals: solubility decreases as you move down the group in the periodic table, making BaSO_4 less soluble than CaSO_4.
Conclude that Ba^{2+} is the ion most likely to form an insoluble sulfate compound because BaSO_4 has very low solubility compared to sulfates of the other ions listed.
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