The estimated lattice energy for CsF21s2 is +2347 kJ/mol. Use the data given in Problem 6.86 to calculate an overall energy change in kilojoules per mole for the formation of CsF21s2 from its elements. Does the overall reaction absorb energy or release it? In light of your answer to Problem 6.86, which compound is more likely to form in the reaction of cesium with fluorine, CsF or CsF2?

Question

Table showing energy values for copper and chlorine in the Born Haber cycle.

Accepted Answer

Welcome back everyone. The lattice energy of copper to chloride solid is 2824 kg per mole. Used the born Haber cycle to determine the entropy of formation for copper to chloride solid from its elements compare this with the entropy of formation for copper one chloride being negative 37.2 kg per mole and determine which compound is more stable. So we're going to recall that we would determine the entropy of formation of our copper to chloride by taking first the information from our born Haber cycle where we're going to take the some of the entropy of sublimation for our solid copper. And added to that, we would have our first ionization energy for copper gas which is then added to our second ionization energy of copper caddy on in gaseous form which is then added to the bond dissociation energy of our chlorine gas then added on 22 multiplied by the electron affinity of our chlorine gas and then added onto that. We would have our Lattice energy of our copper to chloride solid. So we have all of these variables given to us in our chart in the prompt so we're going to set this equal to and plug in each of the corresponding values. So beginning with the entropy of sublimation of solid copper. That's given as 337.4 kg jewels Permal. And as we stated, added onto this, we have our first ionization energy given in the prompt as 745.5 kg Permal. And then we have given our second ionization energy for copper gaseous cat ion of 1957.9 kg per mole added on to this. We have our bond association energy for chlorine gas given as to 42.6 kg per mole. And then added on to this, we have two multiplied by our electron affinity of our chlorine gas given as negative 3 48. kg joules Permal. And then last added onto this, we have our lattice energy given in the prompt for our copper to chloride solid, as negative 2824 killer joules per mole. So simplifying this by taking our entire some we're gonna end up with a value of negative 2 37.8 kg joules per mole. And this would be our entropy of formation of copper to chloride. But we need to determine between the entropy of formation of copper to chloride and copper one chloride solid, which would be more stable, a more stable compound. And so based on these differing values, we can say that the entropy of formation of our copper to chloride is Less than our entropy of formation of copper one chloride solid. And because it has a more negative entropy of formation, we would say therefore, and let's label this as more negative. Our copper to chloride is more stable and this is because our copper to chloride is going to have greater thermal stability and greater thermal stability will correlate to less energy released during the formation of copper to chloride solid. So our final answer again is that the entropy formation of copper to Clyde is more negative and therefore copper to chloride is a more stable compound. This will complete this example as our final answer. I hope everything I reviewed was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video.

Verified Solution

Key Concepts

Lattice Energy

Born-Haber Cycle

Enthalpy Change