To determine the volume occupied by 0.25 mol of chlorine gas, we need to know the conditions of temperature and pressure. Here's how to approach this problem using the Ideal Gas Law:

Ideal Gas Law:

The Ideal Gas Law is expressed as:

PV = nRT

where:

* P is the pressure (in atmospheres)

* V is the volume (in liters)

* n is the number of moles

* R is the ideal gas constant (0.0821 L·atm/mol·K)

* T is the temperature (in Kelvin)

Solving for Volume:

1. Identify the conditions: You need to be given the temperature and pressure of the chlorine gas. Let's assume the chlorine gas is at standard temperature and pressure (STP):

* T = 273.15 K

* P = 1 atm

2. Plug in the values into the Ideal Gas Law equation:

(1 atm) * V = (0.25 mol) * (0.0821 L·atm/mol·K) * (273.15 K)

3. Solve for V:

V = (0.25 mol * 0.0821 L·atm/mol·K * 273.15 K) / 1 atm

V = 5.6 L

Therefore, 0.25 mol of chlorine gas at STP occupies a volume of 5.6 liters.

Important Note: If the temperature and pressure are different from STP, you will need to use the appropriate values in the Ideal Gas Law equation to calculate the volume.