A chemist is preparing an aqueous solution and needs to determine the solubility of various ionic compounds. At 25°C, which of the following compounds is expected to be soluble in water, forming a homogeneous solution?
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The answer
Correct answer: A. Potassium nitrate (KNO₃) is expected to be soluble in water, as all nitrates and alkali metal compounds are generally soluble.
Tested concept: Solubility rules
Explanation
The solubility rules state that all compounds containing nitrate ions (NO₃⁻) are soluble, and all compounds containing alkali metal cations (Group 1, such as K⁺) are soluble. Therefore, potassium nitrate (KNO₃) is expected to be soluble in water. Silver chloride (AgCl) is insoluble as Ag⁺ is an exception to the general rule that chlorides are soluble. Lead(II) sulfate (PbSO₄) is insoluble as Pb²⁺ is an exception to the general rule that sulfates are soluble. Calcium carbonate (CaCO₃) is insoluble because most carbonates are insoluble, with alkali metal carbonates being the main exception.
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