Which of the following substances are likely to be soluble in water? (a) ZnS (b) AU2(CO3)3 (c) PbCl2 (d) Na2S

Verified step by step guidance

1. Step 1: Understand the solubility rules. Generally, compounds containing alkali metal ions (like Na+) and ammonium (NH4+) are soluble. Nitrates (NO3-), acetates (CH3COO-), and most perchlorates (ClO4-) are soluble.
2. Step 2: Evaluate ZnS. Sulfides (S2-) are generally insoluble except for those of alkali metals and ammonium. ZnS is not an exception, so it is likely insoluble.
3. Step 3: Evaluate Au2(CO3)3. Carbonates (CO3^2-) are generally insoluble except for those of alkali metals and ammonium. Au2(CO3)3 is likely insoluble.
4. Step 4: Evaluate PbCl2. Chlorides (Cl-) are generally soluble, but there are exceptions like AgCl, PbCl2, and Hg2Cl2. PbCl2 is one of the exceptions and is only slightly soluble in cold water.
5. Step 5: Evaluate Na2S. Compounds containing Na+ are generally soluble. Therefore, Na2S is likely soluble in water.

Key Concepts

Solubility Rules

Solubility rules are guidelines that help predict whether a compound will dissolve in water. Generally, ionic compounds containing alkali metals (like sodium) and ammonium ions are soluble, while many sulfides, carbonates, and certain halides are often insoluble. Understanding these rules is crucial for determining the solubility of various substances in aqueous solutions.

Ionic Compounds

Ionic compounds are formed from the electrostatic attraction between positively and negatively charged ions. Their solubility in water depends on the strength of these ionic bonds compared to the interactions with water molecules. Compounds with weaker ionic bonds or those that can form favorable interactions with water are more likely to be soluble.

Hydration Energy

Hydration energy refers to the energy released when ions are surrounded by water molecules. This energy can help overcome the lattice energy of ionic compounds, allowing them to dissolve. A higher hydration energy typically indicates greater solubility, as the energy released during hydration compensates for the energy required to break the ionic bonds in the solid.