Sorry, it is from test #3.

Passage:

For any ideal gas, the number of moles, n, should be equal to the ratio PV/(RT). The graph below shows a plot of PV/(RT) vs. Pext for one mole of several real gases and an ideal gas. The Pext values on the horizontal axis are the external pressures at which the PV/(RT) ratios are calculated; they range from normal (around 1 atm) to very high (1000 atm). For one mole of an ideal gas, PV/(RT) = 1, regardless of the external pressure.

The PV/(RT) curve for one mole of methane (CH4) is typical of most real gases: it decreases to a minimum at moderately high pressures and then rises as pressure increases further. This curve shape is the result of the effects caused by the following characteristics of real molecules: at high pressure, values of PV/(RT)lower than ideal (that is, less than 1) are due predominantly to intermolecular attractions; values of PV/(RT)greater than ideal (that is, greater than 1) are due predominantly to molecular volume.

Q:

When carbon dioxide in a closed container is subjected to external pressures less than 650 atm, the deviation from ideality is primarily due to the fact that:

A. calculated gas pressure is less than actual gas pressure.

B. calculated volume is less than actual volume.

C. actual number of moles is greater than calculated number of moles.

Correct Answer

D. actual gas pressure is less than calculated gas pressure.