Problem 37 - Chemistry and Chemical Reactivity

Question

The critical temperature and pressure of chloromethane are \(416 \mathrm{K}\) and 66.1 atm, respectively. (Chloromethane's triple point is at \(175.4 \mathrm{K} \text { and } 0.0086 \text { atm. })\) Can \(\mathrm{CH}_{3} \mathrm{Cl}\) be liquefied at or above room temperature? Explain briefly.

Step-by-Step Solution

Answer

Yes, CH₃Cl can be liquefied at or above room temperature.

Step 1: Determine Room Temperature

Room temperature is typically around 298 K, which is a common reference point for many questions involving temperature.

Step 2: Compare with Critical Temperature

The critical temperature of chloromethane is given as 416 K. Since 298 K is less than 416 K, room temperature is below the critical temperature.

Step 3: Understand Critical Temperature Implication

A substance can be liquefied by pressure alone above its critical temperature, meaning no amount of pressure can turn a gas into a liquid above this temperature.

Step 4: Conclude About Liquefaction

Since room temperature (298 K) is below the critical temperature (416 K), chloromethane can potentially be liquefied at or above room temperature by applying sufficient pressure.

Key Concepts

Liquefaction

Liquefaction is the process where a gas transforms into a liquid. For gases like chloromethane, this transformation depends on two primary factors: temperature and pressure. A gas can become a liquid if it is cooled below its critical temperature while applying appropriate pressure. Otherwise, no amount of pressure will suffice if the gas is above its critical temperature.

• Critical temperature is the highest temperature at which a gas can exist as a liquid. Above this point, the liquid and gas phases cannot exist independently.
• Critical pressure is the pressure needed to liquefy a gas at its critical temperature.

Hence, with chloromethane, even if room temperature is below the critical temperature, additional pressure needs to be applied to achieve liquefaction. This ensures the gas molecules are close enough to create a liquid structure. The critical conditions act as boundaries, guiding scientists and engineers when trying to liquefy gases under different laboratory or industrial conditions.

Chloromethane

Chloromethane, also known as methyl chloride, is a gas at room temperature. It is a colorless substance with a faint, sweet odor. Being an important intermediate in the production of silicon polymers, it's essential to understand its physical properties for its industrial applications.
When considering chloromethane's state in different conditions:

• Its critical temperature is 416 K, and the critical pressure is 66.1 atm.
• It is below its critical temperature at room temperature (298 K), which means it can be liquefied using appropriate pressure.
• Understanding its triple point at 175.4 K and 0.0086 atm also provides insight into how it behaves at different temperatures and pressures.

In practical use, its ability to be easily liquefied at or below the critical temperature makes storage and transportation in liquid form viable when placed under the right pressures, offering convenience in various applications.

Thermodynamics

Thermodynamics plays a pivotal role in understanding the behavior of gases like chloromethane during liquefaction. It governs the laws and observations regarding how temperature and pressure affect the state of substances.
Key principles and laws relevant to this discussion include:

• The first law of thermodynamics, which helps in evaluating energy changes.
• The importance of the critical temperature, where above this temperature, a gas cannot be liquefied just by pressure due to increased kinetic energy.

Thermodynamics bridges the theoretical aspects with practical applications, predicting how gases will behave based on energy changes during temperature and pressure alterations.
In essence, understanding these concepts has industrial significance, ensuring safe and efficient processes for converting gases into liquids by manipulating the environmental conditions around substances like chloromethane.