Select incorrect statement:

Options

A. we can condense vapoor simple by applying pressure
B. to liquefy a gas must lower the temperature below `T_(c)` and also apply pressure
C. at `T_(c)`, there is no distinction between liquid and vapour state hence density of the liquid is nearly equal to density of the vapour
D. However great the pressure applied, a gas cannot be liquified below it's critical temp.

Answer

To solve the question of identifying the incorrect statement regarding the gaseous state, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A: "We can condense vapour simply by applying pressure."**
- This statement is true. Condensation of vapor can occur by increasing the pressure, which forces the gas molecules closer together, allowing them to transition into the liquid state.

2. **Statement B: "To liquefy a gas, one must lower the temperature below Tc (critical temperature) and apply pressure."**
- This statement is also true. The critical temperature (Tc) is the temperature above which a gas cannot be liquefied, regardless of the pressure applied. To liquefy a gas, the temperature must be below Tc, and pressure must be applied.

3. **Statement C: "At Pc (critical pressure), there is no distinction between liquid and vapour state; hence the density of the liquid is nearly equal to the density of the vapour."**
- This statement is true. At the critical point (Pc and Tc), the properties of the liquid and vapor phases become indistinguishable, leading to similar densities for both phases.

4. **Statement D: "However great the pressure applied, a gas cannot be liquefied below its critical temperature."**
- This statement is incorrect. A gas can be liquefied below its critical temperature if sufficient pressure is applied. The critical temperature is the upper limit for liquefaction, not the lower limit.

### Conclusion:
The incorrect statement is **D**: "However great the pressure applied, a gas cannot be liquefied below its critical temperature."

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