The graph below shows the change in pressure as the temperature increases for a 1-mol sample of a gas confined to a 1-L container. The four plots correspond to an ideal gas and three real gases: CO2, N2, and Cl2. (a) At room temperature, all three real gases have a pressure less than the ideal gas. Which van der Waals constant, a or b, accounts for the influence intermolecular forces have in lowering the pressure of a real gas?

Video transcript

Hi everyone. This problem reads the following diagram is a plot of volume against temperature for four gasses. Line K represents an ideal gas, while lines L. M and N represent three real gasses, it can be observed from the graph that real gasses have smaller volumes than ideal gas. Which of the two Vander Wall's constants A or B. Account for this behavior of the real gas. So we want to know which constant accounts for the behavior of real gasses having a smaller volume than ideal gasses. Okay, so let's take a look at our Vander wal's equation and our Van der Waals equation is the following. And in our vendors wild equation here are the two variables A and B. So let's talk about them. Okay, these are the two constants. The constant A. This constant accounts for inter molecular attractions. Okay, so abbreviate that and this accounts for the inter molecular attractions between the molecules of real gasses and our constant. Be accounts for the moller volume of a real gas. So, for our constant A. Due to the inter molecular forces of attractions, the actual pressure of a real gas is always smaller than the one calculated from the ideal gas equation. So we're going to say the pressure is smaller, Okay, on the other hand, for our constant be the molecules of real gasses have a volume of their own as opposed to the kinetic molecular theory. So, due to the molar volume, the volume occupied by a gas is always smaller than the one calculated from the ideal gas equation. So, when the question asks which of the two Vander wal's constants, A or B. Account for this behavior of the real gasses having smaller volumes than the ideal gas, it's going to be the constant. Be accounts for the lower volume. Okay, so let's go ahead and write that constant B. Alright, so that is it for this problem. I hope this was helpful.