Predict which substance in each pair has the highest surface tension. (a) CCl4 or CH2Br2

Video transcript

Hello everyone today. We have a phone problem which of these compounds carbon dioxide or sulfur dioxide will have a higher surface tension. So first let's define what surface tension is. So surface tension is essentially the resistance of a liquid to increase its surface area. So it's the resistance of a liquid to increase its surface area. And so a general trend with surface area is the stronger the inter molecular forces or the forces that exist between molecules, the higher the surface tension. Right? So the strongest inter molecular forces hydrogen bonding. So those hydrogen bonding is going to increase that resistance of a liquid to increase the surface area. So first we have a carbon dioxide, Alright, we have a carbon. Carbon is a group for a element and therefore has four valence electrons. Oxygen is a group six a element and therefore has six valence electrons. However, there are two of them here. So we have 12 and in a total This gives us 16 valence electrons to use for the structure. Now carbon dioxide is going to be a structure with the carbon in the middle double bonded on both sides to an oxygen element. Then oxygen is going to have four electrons bonded to complete its octet of eight electrons. And so according to periodic trends, oxygen is more electro negative than carbon. So we're gonna draw a dipole moments from carbon to oxygen. And by electro negativity trends, it's essentially the higher and more to the right we go to the periodic table, the higher the electro negativity of an element. And so we look at the geometry of carbon dioxide and we note that the geometry is going to be linear, which essentially is going to be that the dye poles or are red arrows that signify electron density are going to cancel out. And if they cancel out, there's going to be a non polar molecule. Next we move on to our sulfur dioxide where we have sulfur, which is a six A element that has six valence electrons and then we have oxygen. That's also a group six element that has six valence electrons. However, there are two. So we end up with 12 here and in total, We end up with having 18 valence electrons. Now this structure is going to be a little different. And why is that? Well, similarly to the previous structure, sulfur is going to be in the center and it's going to be double bonded to two oxygen's. However, it's going to be at a bent angle. And so why is that? Well, this lone pair that's gonna go on that sulfur is going to repel the electrons that are present in these bond lines. And therefore it kind of pushes those bond lines down. So when we draw the diaper moments and in this case the electron density will be going towards oxygen because of that electro negativity trend. This geometry is going to be known as vent and in a bent shape, the dye pole moments, The dyp holes don't cancel. So they don't cancel out. And because they don't cancel, this leads us to have a polar molecule, and so a polar molecule will essentially have higher surface tension, giving us our answer of sulfur dioxide, having a higher surface tension. And with that we've answered the question overall, I hope this helped, and until next time.