The electron affinity of oxygen is -141 kJ/mol, corresponding to the reaction O(g) + e^- → O^-(g). The lattice energy of K₂O(s) is 2238 kJ/mol. Use these data along with data in Appendix C and Figure 7.10 to calculate the 'second electron affinity' of oxygen, corresponding to the reaction O^-(g) + e^- → O^2-(g)

Video transcript

Hi everyone for this problem. It reads given the first electron affinity of sulfur is 200 kg per mole. And the lattice energy of sodium sulfide is negative 2304 kg jewels per mole. What is the second electron affinity of sulfur? So, we want to solve for the second electron affinity of sulfur. Okay. And let's go ahead and define what this means. So first electron electron affinity is the addition of an electron to a neutral atom. Okay, so we're adding this electron to the neutral sulfur. Second electron affinity is the addition of an electron to a negative ion. So here we can see we have an electron that we're adding to a negative ion. So we're being asked for the second electron affinity of sulfur. Okay, so let's go ahead and get started in order for us to go from to gas gaseous sodium. We need to start off with a solid. Okay, so we have two moles of solid sodium Is going to go is going to produce two moles of gaseous sodium. And in terms of our standard heat of formation, our standard heat of formation is going to be multiplied by two. Okay, because we have two most. So the standard heat of formation of sodium Is 107. So we have 107 times two. gives us 214. Okay, so now with that two moles of gaseous sodium, we're going to add two electrons. Okay, so our ionization energy Is also going to be multiplied by two. So our organization energy is 496. And that multiplied by two is going to give us kg joules per mole. So let's go ahead and do the same thing for our sulfur. So are solid sulfur is going to produce our gaseous sulfur. And the heat of formation for this is equal to 279 kg jewels per mole. And so for our gasses sulfur when we add an electron so that it becomes s minus our activation energy. We're told in the problem is negative 200. Okay, and this is X. A thermic. So we need to figure out what is our second activation energy. Okay, so when we have the sulfur and we add an electron, so it becomes us to minus what is our second activation energy. Okay, We don't know what that value is, but we can solve it because we were given the lattice energy. Okay. And so we have our two moles or Yes, we have our two moles of our sodium ion plus S - Gas. And we're told that this reaction has a lattice energy Equal to Negative 2304. And so we can solve for our heat of formation. Okay, so this two moles of solid sodium plus our solid sulfur gives us the sodium sulfide with a standard heat of formation of negative 3 70. So using this we can create an equation to solve for our second electron affinity. Okay. And that equation is going to be based off of everything that we're given. Our heat of formation is equal to our lattice energy plus our second activation energy plus our first activation energy plus our heat of formation of sulfur plus Our Ionization Energy Times two Plus our heat of formation Of Sulfur Times two. So we're going to rearrange this so that we're solving for our second ionization energy. And when we rearrange it, we will get the following. Okay, so we'll get this and we have all of the values that we need to plug in so that we can solve for our second ionization energy. Yes. Our activation energy. Okay. Which is going to be our electron affinity. So that is going to equal once we plug everything in. So our final answer is going to be 649 kg jewels per mole. And this is our final answer. This is going to be the electron affinity. The second electron affinity. Okay, that's the end of this problem. I hope this was helpful