Hess's law can be used to calculate reaction enthalpies for hypothetical processes that can't be carried out in the labo- ratory. Set up a Hess's law cycle that will let you calculate ∆H° for the conversion of methane to ethylene: 2 CH4(g) → C2H4(g) + 2 H2(g) You can use the following information: 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(l) ∆H° = -3120.8 kJ CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) ∆H° = -890.3 kJ C2H4(g) + H2(g) → C2H6(g) ∆H° = -136.3 kJ H2O(l) ∆H°f = -285.8 kJ/mol

Video transcript

Hi everyone here we have a question asking us to determine the entropy of the reaction. Using Hess's law. Iron sulfide plus five halves, oxygen forms iron oxide plus two sulfur oxide. Given the following data. So let's go through each of these. So we have iron plus two sulfur forms iron sulfate and its entropy is negative 178.2 kg joules per mole. So we need to reverse that to match our reaction. So that is 178 point to kill jules Permal. And then we have iron plus half oxygen forms iron oxide and its entropy is negative 272.0 kg joules per mole. And we're just going to keep that one the same. So that will be negative, 272 zero kg Permal. And lastly we have sulfur plus oxygen forms sulfur dioxide And it's info p is negative, 296.8 kg joules per mole. And we need to multiply by that by two to match our reaction. So that will be negative .6 kg per mole. So now we have to add this all up to get our entropy. So that's going to equal 178 points to kill jewels per mole plus - zero killed jules Permal plus -593 . Killed Jules, Caramel. And that equals negative .4 Kill Jules Permal. And that is our final answer. Thank you for watching. Bye