Critical temperature of ` CO_2` is 31.2` ""^(@) C ` . In summer , the room temperature is ` 40 ""^(@) C ` , then

Options

A. ` CO_2` cannot be liquefied
B. ` CO_2` can be liquefied with increase of pressure
C. `CO_2` can be liquefied with decrease of pressure
D. ` CO_2 ` can be liquefied if temperature of `CO_2` is decreased below ` 31.2""^(@) C `

Explanation

To solve the problem regarding the liquefaction of CO2 at a room temperature of 40°C, we can follow these steps:

### Step 1: Understand Critical Temperature
The critical temperature of a substance is the highest temperature at which it can exist as a liquid. Above this temperature, no amount of pressure can liquefy the gas.

### Step 2: Identify Given Values
- Critical temperature of CO2: 31.2°C
- Room temperature in summer: 40°C

### Step 3: Compare Room Temperature with Critical Temperature
We need to compare the room temperature (40°C) with the critical temperature of CO2 (31.2°C).

### Step 4: Analyze the Situation
Since the room temperature (40°C) is higher than the critical temperature (31.2°C), CO2 cannot be liquefied at this temperature, regardless of the pressure applied.

### Step 5: Conclusion
Therefore, at a room temperature of 40°C, CO2 cannot be liquefied.

### Final Answer
CO2 cannot be liquefied at 40°C.

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