Final answer:
The pressure range for flash distillation in a two-component equimolar mixture occurs between the vapor pressures of the two components, so the range is from P₁ to P₂ where P₁ is above the pressure of the more volatile component and below that of the less volatile component.
Step-by-step explanation:
For a two-component equimolar mixture, the pressure range over which a flash can occur is given by the pressures between the vapor pressures of the two components. The more volatile component will have a higher vapor pressure, and the less volatile component will have a lower vapor pressure. Hence, flash distillation can occur at pressures above the vapor pressure of the more volatile compound, but below the vapor pressure of the less volatile compound.
Given that P₁ is greater than the vapor pressure of the more volatile component but less than the vapor pressure of the less volatile component, the correct answer is option a) P₁ to P₂, because P₂ would be at or above the vapor pressure of the less volatile component.