Which of the following substances is insoluble in water?

• A. K_2SO_4
• B. NH_4Br
• C. NaNO_3
• D. AgCl

Answer: (D)

Verified step by step guidance

1. Understand the concept of solubility: Solubility refers to the ability of a substance to dissolve in a solvent, such as water. Ionic compounds that dissociate into ions in water are generally soluble, but there are exceptions based on the ions involved.
2. Recall common solubility rules for ionic compounds in water: For example, most alkali metal salts (like K\_2SO\_4 and NaNO\_3) and ammonium salts (like NH\_4Br) are soluble in water. These rules help predict whether a compound will dissolve.
3. Analyze each given compound using solubility rules: K\_2SO\_4 contains potassium (an alkali metal) and sulfate ions, which are generally soluble. NH\_4Br contains ammonium and bromide ions, both typically soluble. NaNO\_3 contains sodium and nitrate ions, both highly soluble.
4. Consider AgCl: Silver chloride (AgCl) is known to be an exception to many solubility rules because it is poorly soluble in water, forming a precipitate rather than dissolving significantly.
5. Conclude that among the listed substances, AgCl is insoluble in water, while the others are soluble based on the solubility rules.