The solubility of a speific non-volatile salt is 4 g in 100 g of water at `25^(@)C. If 2.0 g, 4.0 g and `6.0 g of the salt added of 100 g of water at `25^(@)`, in system X, Y and Z. The vapour pressure would be in the order:

Options

A. `X lt Y lt Z`
B. `X gtY gtZ`
C. `Z gtX =Y`
D. `X gt Y = Z`

Answer

To determine the order of vapor pressure for the systems X, Y, and Z, we need to analyze the solubility of the salt in each system and how it affects the vapor pressure of the solution.

### Step-by-Step Solution:

1. **Understand the Solubility**:
The solubility of the salt is given as 4 g in 100 g of water at 25°C. This means that at this temperature, a maximum of 4 g of the salt can dissolve in 100 g of water.

2. **Analyze Each System**:
- **System X**: 2 g of salt is added to 100 g of water.
- Since 2 g is less than the solubility limit (4 g), all of it will dissolve.
- This results in a dilute solution.
- **System Y**: 4 g of salt is added to 100 g of water.
- Since 4 g is equal to the solubility limit, this will create a saturated solution.
- **System Z**: 6 g of salt is added to 100 g of water.
- Only 4 g will dissolve (the solubility limit), and the remaining 2 g will remain undissolved.
- This also results in a saturated solution.

3. **Determine Vapor Pressure**:
- The vapor pressure of a solution is affected by the concentration of the solute. According to Raoult's law, the vapor pressure of a solvent decreases when a non-volatile solute is added.
- In a dilute solution (System X), the concentration of the solute is low, leading to a higher vapor pressure compared to saturated solutions.
- In saturated solutions (Systems Y and Z), the concentration of the solute is higher, leading to lower vapor pressures.

4. **Compare the Systems**:
- System X has the highest vapor pressure because it has the least amount of solute (2 g).
- Systems Y and Z have the same amount of solute dissolved (4 g), thus they will have the same vapor pressure, which is lower than that of System X.

5. **Order of Vapor Pressure**:
Therefore, the order of vapor pressure from highest to lowest is:
- **X > Y = Z**

### Final Answer:
The vapor pressure would be in the order: **X > Y = Z**.