Final answer:
The molar volume (Vm) will double if the chlorine pressure (P cl) is changed to 0.5 atm, assuming that the temperature and the number of moles remain constant, due to the inverse proportional relationship between pressure and volume described by the Ideal Gas Law.
Step-by-step explanation:
When considering the change in molar volume (Vm) due to a change in chlorine pressure (P cl), we can refer to the Ideal Gas Law, which states PV = NkT. If the pressure of chlorine (P cl) is changed to 0.5 atm and if the temperature and number of moles remain constant, the volume would have to adjust to maintain the equation's balance. Since the pressure and volume are inversely proportional in this relationship, if the pressure is halved, then the volume must double to maintain equilibrium.
If we begin with a pressure P1 and change the chlorine pressure to Pf = 0.5 atm, and if we assume the initial pressure P1 to be 1 atm for this example, the final volume of the gas (Vm) would be twice the initial volume. This conclusion is drawn from the inverse relationship between pressure and volume when the temperature is held constant.