Final answer:
Changing P NA to 0.4 indicates a change in pressure that, per the ideal gas law, results in an inversely proportional change in volume (V m), assuming that temperature and moles of gas remain constant.
Step-by-step explanation:
When P NA is changed to 0.4, it implies a change in partial pressure of a gas component in a mixture. In a scenario where volume, temperature and number of moles (n) are held constant, but pressure is changed, we refer to the ideal gas law, PV = nRT. Since n, R (ideal gas constant), and T (temperature) are constant, V (volume) must be inversely proportional to P (pressure). Therefore, if P NA is changed from its original value to 0.4, this decrease in pressure results in an increase in the molar volume, V m, of the gas. The exact new volume can be calculated using the equation V₂ = V₁(P₁/P₂), where V₁ and P₁ are the initial volume and pressure values, and V₂ and P₂ are the final values, with P₂ being 0.4 in this case.