Consider the generic reaction: A + 2 B¡C + 3 D ΔH = 155 kJ Determine the value of ΔH for each related reaction. a. 3 A + 6 B¡3 C + 9 D b. C + 3 D¡A + 2 B c. 12 C + 32 D¡12 A + B

Video transcript

hey everyone in this example we're given the above reaction and the entropy of negative 200 kg joules. We need to find the entropy change of each of these given reactions. So for our first reaction we have two moles of C reacting with one mole of D. To produce two moles of A. And two moles of B. As you can see in our original reaction here we have two moles of A and two moles of B on the reactant side. And so this means that our reaction was reversed. So because our reaction was reversed, we're going to go ahead and also find r N therapy by therefore flipping our sign of entropy. So we would say our entropy is going to equal negative 200 kg joules times negative one. And so this would equal a value of positive 200 kg joules. So this is our first answer for part one of this question. Moving on to part two, we should recognize that we have formals of a reacting with formals of B. To produce formals of C. And two moles of D. As you can see this is double the amount of each of our agents in our original equation. And so to find the entropy of part two, we would say that entropy is going to equal double the amount of our original entropy negative 200 kg joules. So we would multiply this by two and this gives us a value of negative 400 kg joules. As our second answer for this example moving on to Part three we have six moles of re agency reacting with three moles of reagent D. To produce six moles of reagent A. And six moles of reagent B. And as you can see again our re agents are flipped. So we also reverse this reaction, meaning we should flip the sign of our entropy value. And we also have tripled our amounts of our re agents compared to our original equation. So we would go ahead and calculate our final entropy by multiplying by negative three To the original entropy value of -200 kg jewels. And this is ultimately going to flip the sign to a positive entropy value equal to 600 kg jewels. And so this would complete this example as our third and final answer. So if you have any questions, please leave them down below. Otherwise I hope everything we went through is clear and I'll see everyone in the next practice video.