Which of the following reactions in the stratosphere cause an increase in temperature there? (a) O(g) + O2(g) → O3+(g) (b) O3*(g) + M(g) → O3(g) + M*(g) (c) O2(g) + hv → 2 O(g) (d) O(g) + N2(g) → NO(g) + N(g) (e) All of the above

Video transcript

Hey everyone today, we're being asked to see which of the following combinations of reactions will increase the temperature of the chamber that the reactions are taking place in. So we're given four separate reactions 123 and four. And the answer choices each give us a combination of two of them and we're asked to find out which one will raise the total temperature of the chamber that they're taking place in. Right? So to do this, we need to identify if the reactions are endo thermic or exo thermic. Remember that endo thermic, endo thermic reactions which are right in blue and thermic absorb heat, absorb heat from the surroundings, absorb heat. Usually form bonds and change. And if there is a change of phase it'll usually go from a higher energy phase. Like a gas to a lower energy phase like a solid or liquid bonds form and the surroundings. Well, cool. Well, cool, eggs are thermic reactions are the exact opposite. Exo thermic reactions will release heat into the, into the surroundings, release heat and bonds will be breaking because when a bond breaks, the energy in that is released usually has heat so bonds will break break and the surroundings will heat up surroundings will heat up. So what this means is we need to find the combination of reactions in which both our exo thermic. So let's take a look at each one. So for the first problem for the first question I guess We're dealing with carbon dioxide and water forming glucose C6, H 1206 and oxygen gas. Now we're starting off with a gas and a liquid and it's becoming as solid and a gas. So the state or the phase change is going down and yeah going down energy is becoming more stable. And we're also forming bonds between carbon dioxide and water. So what this means is that we're dealing with an endo thermic reaction. This is endo thermic meaning that the surroundings will end up getting cooler. Let's take a look at the next one we're doing with Hc 03 H plus reacting with each other in order to form water and carbon dioxide. So in this case we're dealing with the neutralization process of a weak acid. H. C. 03 gets added with H plus to form water and C. +02. So since bonds again are forming between the H plus and the H. C. +03 minus. We're again dealing with an endo thermic reaction and the surroundings will cool. Endo thermic for option three. Now we have a church to as a liquid and hcl or hydrochloric acid forming hydro ni um and cl minus. So this is a water reacting with an acid and as such, the bond between H and cl will actually get broken. And furthermore, we're going from liquid and Aquarius to full Aquarius but that doesn't really matter. Everything is still liquid. But since the acid is reacting with the water there will be heat generated from the reaction as the bonds are being broken and then reformed later. So this will be an exo thermic reaction. The system will actually lose heat to the surroundings so the surroundings will actually heat up Finally the very last option is actually the complete reverse of option one. We're starting with glucose and oxygen to form carbon dioxide and water. And this is photosynthesis. This is photo synthesis but we're going from solid and gas to gas and liquid. So the phase is changing into a less stable or higher energy phase. And since bonds are being broken, the bonds and glucose are being broken to form carbon dioxide and water, that just means that we're dealing with an extra thermic reaction that makes the surroundings hotter will increase the temperature of the chamber. So with all this in hand, let's look at the answer choices now. So answer choice A Says one and 2 when reacted separately in the chamber will increase. Well this is of course incorrect because they're both endo thermic, which means both reactions will end up cooling down the chamber. So this is incorrect. One in three seems promising because now it's an endo thermic reaction and A. X. A. Thermic reaction. But because one's increasing temperature and one's decreasing temperature and we don't know by how much what's the magnitude of the change in temperature. This we can safely say that this would have no change in the temperature. So they can rule this out. And option choice C. Is the exact same thing. It's an exo thermic reaction two and three. Or it's an endo thermic and exo thermic being two and three that are reacting together. And we'll have the same dilemma that we had for option choice B. So we can rule that out as well. Now we have two and four, which again is one endo thermic and one exo thermic. So we can safely say that there will be no change in the temperature. Finally answer Choice C, however, has two X atomic reactions. Remember an exo thermic reaction will increase the temperature of the surroundings and since both three and four rxa thermic, that means overall the overall the temperature and the surroundings in the chamber will increase. That means The following reactions three and 4 when reacted separately in a chamber will increase the temperature of that chamber. I hope this helps. And I look forward to seeing you all in the next one.