Indentify the correct order of solubility in aqueous medium

Options

A. `CuS gt ZnS gt Na_2S`
B. `ZnS gt Na_2S gt CuS`
C. `Na_2S gt CuS gt ZnS`
D. `Na_2S gt ZnS gt CuS`

Explanation

To determine the correct order of solubility of ionic compounds in aqueous medium, we can follow these steps:

### Step 1: Understand the Factors Affecting Solubility
Ionic compounds' solubility in water is influenced by several factors, including the size of the cation and anion, the charge of the ions, and the lattice energy of the compound. According to Fajans' rules, smaller cations with high charge tend to have higher ionic character, which can affect solubility.

### Step 2: Identify the Compounds
In the given context, we are considering the solubility of the following compounds:
- Na2S (Sodium sulfide)
- ZnS (Zinc sulfide)
- CuS (Copper(II) sulfide)

### Step 3: Analyze the Cations
- **Na+** (Sodium) is a small cation with a +1 charge.
- **Zn2+** (Zinc) is a smaller cation with a +2 charge.
- **Cu2+** (Copper) is also a small cation with a +2 charge.

### Step 4: Compare the Solubility
Using the principles of ionic character and solubility:
- Na2S will be more soluble in water due to the smaller size of Na+ and its +1 charge.
- ZnS is less soluble than Na2S but more soluble than CuS because Zn2+ has a higher charge which increases lattice energy, making it less soluble than Na2S.
- CuS is the least soluble due to the larger size of Cu2+ and its +2 charge, which leads to higher lattice energy.

### Step 5: Establish the Order of Solubility
Based on the analysis, the correct order of solubility in aqueous medium is:
**Na2S > ZnS > CuS**

### Summary of the Solution
The correct order of solubility in aqueous medium for the ionic compounds Na2S, ZnS, and CuS is:
**Na2S > ZnS > CuS**