Acetylene, C2H2, reacts with H2 in two steps to yield ethane, CH3CH3: (1) HC?CH + H2 → H2C?CH2 ΔH° = -175.1 kJ (2) H2C?CH2 + H2 → CH3CH3 ΔH° = -136.3 kJ Which arrow (a–c) in the Hess's law diagram corresponds to which step, an2d which a2rrow cor2responds to the net reaction? Where are the reactants located on the diagram, and where are the products located?

Video transcript

Hi everyone. This problem reads Consider the following hypothetical reaction between D and E. To form G occurring in two steps. In the following Hess's law diagram, identify the arrow that corresponds to each step and determine the arrow that corresponds to the overall reaction, identify the location of the products and the react ints. Okay, let's start off by looking at our hypothetical reaction. Okay, we can see that F is a spectator ion. It shows up as a product and then as a reactant so we can go ahead and ignore F. So what that means then? If we ignore F is that our overall reaction is going to be D plus two E yields G. Okay, so that's our overall reaction. Looking at our standard entropy change for both. Okay, Looking at our standard entropy change for both. Our standard entropy for step two is greater than The standard entropy change for step one. So that's something else that we're going to want to take a look at. All right, something else that we're going to want to observe is the sign of our change in entropy. Okay, so a positive change in entropy means that the entropy change for the products is going to be higher than the entropy change for the reactant since Okay, and what this means is that the products is higher than the reactant. Okay, so let's continue that here. So we want to look for the image that shows the products being higher than the reactant since Okay, and for the overall reaction. Okay, we're going to look at the sum of our change in entropy. So our change in entropy is going to be 50 kg jewels Permal plus 100 kg joules per mole. So overall our change in entropy is equal to positive. 150 killer joules per mole. So the sign is going to be positive. So those are key pieces of information that we're going to want to look at to identify the arrows that correspond to each step and determine the arrow that corresponds to the overall reaction. So when we take a look at the answer choices given, we want to look for. Where the change in entropy for step two is greater than step one, where the products are higher than the reactant and for our overall the change in entropy is positive. Okay, so out of the answer choices given B is going to be our correct answer that reflects those. Okay, so that is it for this problem. I hope this was helpful.