You have studied the gas-phase oxidation of HBr by O₂: 4 HBr(g) + O₂(g) → 2 H₂O(g) + 2 Br₂(g)

You find the reaction to be first order with respect to HBr and first order with respect to O₂. You propose the following mechanism:

HBr(g) + O₂(g) → HOOBr(g)

HOOBr(g) + HBr(g) → 2 HOBr(g)

HOBr(g) + HBr(g) → H₂O(g) + Br₂(g)

(a) Confirm that the elementary reactions add to give the overall reaction.

Video transcript

Hello everyone today. We are being given a series of steps over an overall reaction and then asked if these two reactions add to give the overall reaction. So in order to even find out what that means, we have to remember two rules. So the first one, is that the same species on the same side? So same species, same side they are going to add. And the second role is that the same species on opposite sides. So opposite sides, you're going to subtract. So same species, same side, you add them, same species on opposite sides, you subtract. So if you write out our step one, we have N 02 in the gas form, adding to N 02 in the gas form to yield an gasses as well as you know, in the gasses, we're then going to react that N. 03 in the gaseous form with carbon monoxide gas to yield N. 02 in the gas form as well as C. 02 in the gas form as well. And so using the same rules are going to get rid of some ions as well as add them together. So, off the bat, we note that N 02 is visible for step one on the left and on step two on the right. And so we also see that N. 03 on the right of step one is also present on the left of Step two. Leaving us with an overall reaction of N. 02 in the gas form of course, plus our C. O. In the gas form yielding us, you know, or nitric oxide, and the gas form, as well as C. +02 in the gas form. And so from the question stem, we have the overall reaction right here, and we can see that yes, they and up to the overall reaction. So yes, the two steps add up to the overall reaction. I hope this helped, and until next time.