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Calculate the $\Delta U$ for the following reaction at $298 \mathrm{K}$ :$$2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)$$

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$\Delta \mathrm{E}=-564.17 \frac{k J}{m o l}$

Chemistry 101

Chapter 6

Thermochemistry

University of Central Florida

University of Maryland - University College

University of Kentucky

Lectures

05:27

In chemistry, a chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Both reactants and products are involved in the chemical reactions.

06:42

In chemistry, energy is what is required to bring about a chemical reaction. The total energy of a system is the sum of the potential energy of its constituent particles and the kinetic energy of these particles. Chemical energy, also called bond energy, is the potential energy stored in the chemical bonds of a substance. Chemical energy is released when a bond is broken during chemical reactions.

02:25

What is $\Delta U$ for the…

02:36

01:47

Calculate $\Delta G^{\circ…

08:11

Calculate $\Delta H$ for t…

03:46

Calculate $\Delta H$ for

03:18

02:50

Calculate $\Delta G$ for t…

03:56

05:05

04:37

So for this problem, we're supposed to find the Delta U for this chemical reaction. And so our overall strategy in solving this problem is going to be using the formula, the change in energy or, in this case, Delta U, legal to heat plus work. This is an expression of the first law of thermodynamics, by the way. So we first need to find the heat with the reaction. And then finally the work done as gas compress or expense, you'll figure out which one that is in the problem. So the first step is we need to find Q. So this is solving cute. So as always, we know that we can find the heat of the reaction by finding the heats of formations, the products amidst the tractor, some of the heats of formations of the reactions. So in this case, this is quite simple because the reactant are all elements in this case hydrogen gas and oxygen gas. And because they're in their natural state heats informations for those are zero and then so the only thing that we need to do is find the heat's information for the products in this case, liquid water. So elements cancel out and this is the only thing we're looking at. So we have two moles of water and we know that the heat of formation of water is negative. 200 and 85 0.8 till jewels, meaning that the queue in this reaction or the heat of this reaction is negative. 500 and 71.6 killed. Jules, promote of reaction. So that is solving for cues. We've done the first part. Now we need to do the second part, which is solving for W for work. So we know that we can express work as this work equals work equals negative or key times Delta end. And so this can help us find the work done as a guest compresses or expands. So we know that our is a constant, which is 8.341 Truls from Okay, we know that the temperature has given to us in the problem is 298. Kelvin, the last thing that we need to find his delta and in this case, Delta and represents the change in guests reactant and products. So let's look at the initial equation that we had so on the left side or the react. Inside, we have three moles of gas reactive because two moles of hydrogen normal auction On the right side, we have zero because the only product is liquid. So we know that we going from 3 to 0. So the change in the moles of gas is negative. Three. So then all we need to do is multiplied all of those numbers together. And then we will get the work done. Use 7000 430 keep in mind that this is a positive value. But just keep our units consistent. We're gonna change this to kill a jewels, because that's what we got for part A. So I want to do is divide by 1000 we get 7.43 villages of all of reaction. So that solves the second part. And so now the only thing that we need to do is we need to just add these values together. So, as we said at the beginning, changing energies keep less. W que is negative. 571 0.6, like resolving per day on the W is 7.430 And when we add these together, you get the Delta E is negative. 500 and 64.2 que joules per mole of reaction, and that is the final answer.

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