All the oxides of nitrogen have positive values of ΔGf° at 298 K,...

Question

All the oxides of nitrogen have positive values of ΔGf° at 298 K,
but only one common oxide of nitrogen has a positive ΔSf°.
Identify that oxide of nitrogen without reference to thermodynamic data and explain.

Accepted Answer

Hello everyone today, we have the following problem. All oxides of sulfur have negative gibbs free energy at 25 degrees Celsius. But only one oxide has a positive entropy of formation at the same temperature, identify the oxide and explain why its entropy of formation is positive. So the first thing we wanna do is you want to note that a positive entropy of formation is indicative of an endo thermic reaction. So we have an endo thermic reaction. And so then we're gonna examine each of these different processes. For example, we're going to have our sulfur monoxide or S. O. And we're gonna be forming that. So what we're gonna do is we're going to have our octo sulfide as a solid. And then we're gonna add that to half a mole of oxygen gas. And this is gonna give us our sulfur oxide in the gaseous form. And so to simply balance this out, we're just gonna say that we have 1/8 of our sulfur octo sulfide. And so with this this is going to require or this process is going to require us breaking. So we're not going to have to break our sulfur sulfur bonds and our oxygen oxygen bonds. However, we are forming our one sulfur oxygen bond. So now we're going to move on to sulfur dioxide. It's going to be a very similar process where we have our 1/ of sulfur solid, with just one mole of oxygen gas to give us sulfur dioxide in the gaseous form. And in this problem, or in this example we are only breaking a sulfur sulfur bond and we are forming two of our sulfur oxygen bonds. And so lastly we have our sulfur trioxide. That's gonna be our 1/8 of our sulfur and the solid form Plus 3/2 of our oxygen gas. And this is going to give us sulfur trioxide gaseous form. And in this equation here we are breaking a sulfur sulfur bond and an oxygen oxygen bond. However, we are forming three sulfur oxygen bonds and so we have to determine which one has a positive. So we said that a positive change of entropy is going to be an endo thermic reaction and endo thermic reaction. We're going to have more bonds breaking. And so out of these answer choices more bonds breaking than forming. So out of these answer choices, we're going to say that sulfur monoxide here, it's going to have a higher entropy change. And to be a formation change because not only are we breaking two bonds here, we're breaking two bonds for sulfur trioxide. However, we are forming one bonds. So the ratio of bonds breaking to forming is going to be greater for sulfur monoxide. And with that we've answered the question overall, I hope this helped. And until next time

All the oxides of nitrogen have positive values of ΔGf° at 298 K, but only one common oxide of nitrogen has a positive ΔSf°. Identify that oxide of nitrogen without reference to thermodynamic data and explain.

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