Based on common solubility rules, which compound is insoluble in water at room temperature?

• A. ${\mathrm{Ag}}_{\mathrm{Cl}}$
• B. $K_2{\mathrm{CO}}_3$
• C. ${\mathrm{Na}}_2{\mathrm{SO}}_4$
• D. ${\mathrm{NH}}_4{\mathrm{NO}}_3$

Answer: (A)

Verified step by step guidance

1. Identify the ions present in each compound: AgCl contains Ag⁺ and Cl⁻; K₂CO₃ contains K⁺ and CO₃²⁻; Na₂SO₄ contains Na⁺ and SO₄²⁻; NH₄NO₃ contains NH₄⁺ and NO₃⁻.
2. Recall the common solubility rules: most compounds containing alkali metal ions (like K⁺ and Na⁺) and the ammonium ion (NH₄⁺) are soluble in water.
3. Note that nitrates (NO₃⁻) are generally soluble, so NH₄NO₃ is soluble.
4. Recognize that most carbonates (CO₃²⁻) are insoluble except those with alkali metals and ammonium, so K₂CO₃ is soluble.
5. Understand that silver chloride (AgCl) is a classic example of an insoluble salt in water at room temperature due to the low solubility of silver halides.