Indicate whether each statement is true or false. (a) Unlike enthalpy, where we can only ever know changes in H, we can know absolute values of S. (b) If you heat a gas such as CO₂, you will increase its degrees of translational, rotational and vibrational motions. (c) CO₂(g) and Ar(g) have nearly the same molar mass. At a given temperature, they will have the same number of microstates.

Video transcript

welcome back everyone in this example. We need to specify whether each claim is true or false. Beginning with statement A. It says that at temperature at a given temperature, sulfur trackside gas and krypton gas will have the same number of micro states because they have almost the same molar mass. So we want to focus on the term micro states and recall that that means the number of possible arrangements and kinetic energies of all molecules in a sample. Sorry, this says sample. So for sulfur trioxide and krypton to have almost the same molar mass, they need to have almost the same number of micro states. Is what statement A is claiming. But if we look at sulfur trioxide, we see that this is a poly atomic molecule, whereas krypton is only mon atomic. So we have more possible arrangements for the kinetic energies of our sulfur trioxide molecule versus just our mon atomic Krypton, we won't have as many arrangements at all. So we're going to say that sulfur trioxide will have more micro states since it's polly atomic And so statement A is going to be false as our first answer. Moving on to statement B, it says that heating a gas like sulfur dioxide will not affect the degrees of translational rotational and vibrational motions. So we want to recall that the translational rotational and vibrational motions are all determined by structure of our molecule. And if we will heat our gas sulfur dioxide, that's going to create additional kinetic energy. And so this additional kinetic energy from heating the gas will therefore give us more will say, well therefore yield more micro states due to this increase in kinetic energy meaning we'll have more arrangements for our structure based on more translational vibrational and rotational motion. So we'll say plus more motion Of the three types. And if we are assuming that heating won't change our structure, then the degrees of freedom of the molecule will not change. And so based on these outlined facts, we're going to consider choice B. To be a true statement. And so that is our second answer. And now we can move on to statement see which says that the absolute values of entropy and entropy can be both determined. We want to recall something known as our bolts Hman relationship where entropy can be found from taking our bolts man constant K. Multiplied by the Ln. Of our multiplicity of our gas from its macro states to its micro states. So based on this fact we can definitely determine an absolute value for entropy but we cannot determine an absolute value for entropy. So we would say that we can only determine changes in entropy so delta H. But we'll just write out the word entropy. So it makes sense notice how in the bolton equation we don't have the delta symbol for the change in entropy but for entropy we're always going to have that delta age symbol and so C. Is going to be considered a false statement as our third final answer to complete this example. I hope everything I reviewed was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video.