In an endothermic chemical reaction, do the products have more mass, less mass, or the same mass as the reactants? Explain.

Video transcript

Welcome back everyone. We need to compare the masses of reactant and products in an endo thermic reaction to those in an exact thermic reaction and provide an explanation. Let's look at choice A. It states that whether a reaction is endo thermic or X. A. Thermic the mass of the reactant is identical to the mass of the products. Now we want to begin by recalling that over the course of a reaction. In comparison between our reaction. Sorry, our reactant versus our products. Energy is going to vary between the two. And Einstein proved this in his formula for energy mass relation where E. Is equal to M. R. Mass times C squared. Being our speed of light squared. And we can see that there's a direct relationship between energy and mass. We also want to recall our law of mass energy conservation which states that the sum of the mass plus energy of our reactant should equal the sum of the mass plus energy of our products. And so we would actually correct statement a to say that the mass of the reactant is equal to the mass of the products. Whether the reaction is endo thermic or exo thermic and you might think that identical means the same thing as equal. But because we understand that equal really means just having the same value as far as mass for products and react ints. That doesn't mean that their energy will be the same. We understand as we stated that energy varies across our reactant to products in a reaction, whether it's endo thermic or eggs, a thermic and so we would actually consider statement A to be false and not a good explanation. So we would rule it out as an answer choice. Now let's move on to answer choice B. It says in an endo thermic reaction, the mass of the reactant is slightly greater than the mass of the products because energy, heat or in the form of heat is released and converted to mass in an exit thermic reaction, the mass of the reactant is slightly less than the mass of the products because the absorption of energy is accompanied by a slight increase in mass. Now here we want to recall that an endo thermic reaction requires an input of energy and this will correspond to energy being absorbed by our react ints. Now because we stated earlier that energy and mass have a direct relationship if energy is being absorbed by the reactant, that should then be followed by the conversion of energy into increasing the mass of our products. Now this should only be observed on a macro scale, meaning that it's only a very slight increase. And so we would consider that statement be should be corrected to say that energy is going to be absorbed by the reactant and because it's then converted to mass, that would make the mass of our products more slightly larger. And so we would correct the beginning of the sentence to say that the mass of the reactions would be slightly lower. Or we can say less than the mass of the products, which as we stated, increase on a macro scale. Now on the second half of this sentence, it says in an X. A thermic reaction, the mass of the reactant is slightly less than the mass of the products because the absorption of energy is accompanied by a slight increase in mass. Let's recall that in an exo thermic reaction, energy in the form of heat is released to our products. However, a very small amount of energy will be conserved as mass for our reactant and so therefore this will increase the mass of our reactant also on a macro scale. So we would correct the second half of the sentence to say that the mass of the reactant is slightly greater than the mass of the product because energy is going to be released while some is conserved and accompanied by a slight increase in mass of our reactant. So be we would consider also a false statement and we would rule it out since we had to correct the statement. Let's move on to choice C There is no trend for the massive reactant versus the massive products between an endo thermic and an exit thermic reaction. Now, as we stated earlier, our energy mass relation formula E equals M C squared was proved by scientists like Einstein in which specifically are massed effect delta M, which is determined by the sum of the mass of our products minus the sum of the mass of our reactant. Which helps prove the pattern of the relationship between mass defect between our reactant and products and energy. And this is due to the fact that our mass defect is our measure of missing mass, quote unquote that has been converted into energy through the binding energy of the nucleus of an atom. And recall that binding energy is energy required to separate protons and neutrons into separate free particles. And so are massed effect ultimately provides the empirical validation of the relationship between E equals M C squared, or the relationship specifically between energy and mass in our universe. We also want to think of our law of conservation of energy and mass, which also proves this relationship and pattern. And so we would actually rule out c as a false statement, since there is a pattern that is observed and proved by scientists via what we've outlined in our notes and now moving on to example, D or Choice D rather, it says that in an endo thermic reaction, the mass of the reactant is slightly less than the mass of the products. So the mass of the products would be increasing then because energy in the form of heat is absorbed by the reactant. So it seems like energy is increasing and is converted to mass. And that completely goes in line with what we outlined above here, where we said that an endo thermic reaction because requires an input of energy will therefore correspond to energy being absorbed by our reactant. And therefore with that increase of energy we have an increase in mass for our products on a macro scale. And so yes, the mass of the reactant will thus be slightly less. So we can actually agree with the first sentence in choice D. Moving on to the second part of choice T. It says that in an X. A. Thermic reaction, the mass of the reactant is slightly greater than the mass of the products. So that tells us that the mass of the product will decrease because the release of energy. So energy is decreasing is accompanied by a slight loss and mass. And so this also falls in line with what we outlined for an exo thermic reaction where energy will be released to our products, where some of that energy is reserved via conservation of mass for our reactant, thus increasing the mass of our reactant on a macro scale. And so we can also agree with the second part of example D. Meaning that we can confirm it to be a true statement and is therefore the best explanation for why the masses of reactant and products and an endo thermic reaction can be compared to be slightly greater or less depending on the energy exchange of the type of reaction. And so choice D is our final answer. To complete this example. I hope that everything I reviewed was clear. But if you have any questions, leave them down below and I'll see everyone in the next practice video.