Passage VI

The ideal gas law (IGL) describes the physical behavior of gases. Although ideal gases do not exist, the IGL is a useful model for many real gases. A researcher used the IGL to predict trends in the pressure of an ideal gas under various sets of conditions. Then, the researcher performed 3 experiments to compare the IGL predictions with trends in the pressure of each of 2 real gases (Gas Y and Gas Z) under the same sets of conditions. The conditions that were varied for an ideal gas, for Gas Y, and for Gas Z were the following:

·The gas temperature, T (in kelvins, K)

·The amount of gas, n (in moles, mol; 1 mol=6.0 x 1023 atoms or molecules), in a container

·The volume of the container, V (in liters, L)

Experiment 1

The pressure, P (in megapascals, MPa), of an n=1 mol sample of Gas Y in a 1.0 L container was recorded for values of T from 200 K to 450 K. This procedure was repeated for Gas Z. Figure 1 shows the trends for the 2 gases. Also shown is the trend predicted by the IGL.

Experiment 2

The pressure, P, of a sample of Gas Y in a 1.0 L container was recorded for values of n from 1 mol to 10 mol, while T was held constant at 400 K. This procedure was repeated for Gas Z. Figure 2 shows the trends for the 2 gases and the trend predicted by the IGL.

Experiment 3

The pressure, P, of an n=1 mol sample of Gas Y in a container of adjustable volume was recorded for values of V from 0.5 L to 1.0 L. while T was held constant at 400 K. This procedure was repeated for Gas Z. Figure 3 shows the trends for the 2 gases and the trend predicted by the IGL.

40. Consider an n = 1 mol sample of Gas Z at 400 K in a 1.0 L container of adjustable volume. Suppose the researcher must decrease the container’s volume, but wishes to hold P constant. Based on the results of Experiments 1-3, which of the following additional actions should the researcher perform simultaneously as V is decreased?

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

It can be seen from figure 3 that the gas pressure will increase as the container volume decreases; and from figure 1 and figure 2, it can be seen that the gas pressure will increase with the decrease of temperature T and mole number n Small and reduced. Therefore, when the volume of the container becomes smaller, the gas pressure will increase. In order to keep the pressure constant, it is necessary to lower the temperature or increase the number of moles of the gas, so only option F is feasible