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Ch.15 - Chemical Kinetics

Chapter 15, Problem 27a

For the reaction 2 A(g) + B(g) → 3 C(g), a. Determine the expression for the rate of the reaction in terms of the change in concentration of each of the reactants and products.

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Hi everyone for this problem, we are asked to write the rate expression in terms of change in concentration of each reactant and product for the following reaction. Okay, so our goal here is to write a rate expression in terms of change in concentration. Okay, so let's recall what rate is, So rate is equal to change in concentration over change in time. So looking at our reaction here, we're going to use this to write our rate expression. And what our rate expression tells us is that as for our reactant, as time goes on, the concentration of reactant is going to decrease and as time goes on, the concentration of products is going to increase. So our rate is going to equal, let's take a look at our first reactant. We have a and we only have one mole of it. So it's going to be the change in concentration of a over change in time. And because our as time goes on, the concentration of reactant decreases, we're going to put a negative here and looking at the stoke eom a tree, we only have one mole, so we can just leave it as is okay, so for our second reactant, we have three moles of B. And so our rate is going to be the change in concentration of B is over. Our change in time. And because this is a reactant, the concentration is decreasing, but we need to look at the stoke eom a tree here, we have three moles of B. So this three moles is going to change into a fraction. So we're going to have negative one third. Okay, And our product here is four moles of C. So we're going to have our change and concentration of C over our change in time. And because as time increases, the concentration of products is increasing, this is going to be a positive. And looking at the stoke eom Attar, we have four moles of C, so this converts to 1/4 and this is going to be a positive value. Okay, so this is going to be our rate expression, Okay, And this is going to be our final answer. So that is the end of this problem. I hope this was helpful.