Question

A gas at 350 K and 15 bar has molar volume 20 percent smaller than that for an ideal gas under the same conditions. The correct option about the gas and its compressibility factor (Z) is :

• A. Z< 1 and attractive forces are dominant
• B. Z < 1 and repulsive forces are dominant
• C. Z > 1 and attractive forces are dominant
• D. Z > 1 and repulsive forces are dominant

Answer 1

The Correct Option is A

The question revolves around the concept of the compressibility factor (Z) for gases, which is a measure of deviation from ideal gas behavior. The given conditions are:

• A gas at 350 K and 15 bar.
• The molar volume is 20% smaller than that of an ideal gas under the same conditions.

Let's break down the explanation using the compressibility factor formula:

The compressibility factor, Z, is defined as:

Z = \frac{PV}{nRT}

For an ideal gas, Z = 1. If Z \neq 1, the gas does not behave ideally.

Key Points:

1. If Z < 1, it implies that the gas particles are interacting attractively more than they would in an ideal state, reducing the effective volume. This indicates attractive forces are dominant.
2. If Z > 1, it suggests that repulsive interactions are prevalent, increasing the effective volume.

Given that the molar volume is 20% smaller than for an ideal gas, this implies:

Z < 1

Thus, the compressibility factor Z < 1 indicates that the attractive forces within the gas are dominant.

Considering this analysis, the correct option is:

Z< 1 and attractive forces are dominant

Therefore, the correct answer is: Z< 1 and attractive forces are dominant.