Question

A gas cannot be liquefied if (1) forces of attraction are low under ordinary conditions (2) forces of attraction are high under ordinary conditions (3) forces of attraction are zero under ordinary conditions (4) forces of attraction either high or low under ordinary conditions

Short answer

(3) forces of attraction are zero under ordinary conditions

Step-by-step solution

Understand the Concept of Gas Liquefaction

Gas liquefaction refers to the process of converting a gas into a liquid by cooling or compressing it. The ability to liquefy a gas depends on the intermolecular forces of attraction among its molecules.

Analyze the Role of Intermolecular Forces

Recognize that stronger intermolecular forces make it easier to bring gas molecules close together, hence facilitating liquefaction. Conversely, weaker intermolecular forces would make this process more difficult.

Evaluate Each Option

Consider each given option: (1) Low forces of attraction under ordinary conditions mean it's more likely to be difficult to liquefy the gas. (2) High forces of attraction make liquefaction easier. (3) Zero forces of attraction would make the molecules very difficult to bring close together, preventing liquefaction. (4) Forces of attraction, whether high or low, would not provide a definitive condition for preventing liquefaction.

Choose the Correct Answer

Based on the evaluation, the correct answer is that a gas cannot be liquefied if the forces of attraction are zero under ordinary conditions, as this would make it impossible for molecules to come close enough to liquefy.

Key concepts

intermolecular forces

To understand gas liquefaction, knowing about intermolecular forces is essential. These are the attractive forces between molecules. There are different types, like Van der Waals forces, dipole-dipole interactions, and hydrogen bonds.

When intermolecular forces are strong, molecules are more tightly glued to each other. This tight bonding means it is easier to compress the gas and turn it into a liquid. Why? Because strong forces help to bring molecules close together and lock them in place.

On the other hand, if these forces are weak, the molecules are more free to move around. They won’t easily come together, making gas liquefaction tougher. If there are zero forces of attraction, gas molecules will not come close at all, making liquefaction impossible.

compressing gas

Compressing gas is one of the primary methods used in gas liquefaction. By applying pressure, we force the gas molecules into a smaller volume.

Think of it like squeezing a sponge: the closer the molecules come together, the more likely it is they’ll turn into a liquid. But remember, compressing alone might not be enough. The intermolecular forces need to be strong for full liquefaction to occur.

Here's a useful fact: Gases like carbon dioxide and ammonia, with relatively strong intermolecular forces, can be compressed more easily into liquids compared to gases like helium or hydrogen, which have very weak intermolecular forces.

cooling gas

Cooling gas is another key method to achieve liquefaction. By lowering the temperature, we reduce the kinetic energy of the gas molecules. When molecules lose energy, they move more slowly and are more likely to stick together.

Imagine slowing down a dance to a stop; when people move slower, they are closer to one another. Similarly, cooling a gas can make it easier for molecules to be attracted to each other and form a liquid.

Important Tip: Cooling is especially useful when dealing with gases that don’t compress well. Combining both cooling and compressing often yields the best results in terms of gas liquefaction. Still, the influence of intermolecular forces cannot be overstated as they play a vital role in this entire process.