8.61 Question

$\Delta U=q+w$

Frenz Cabison 1B
Posts: 54
Joined: Fri Sep 29, 2017 7:07 am

8.61 Question

So the question was:

And here is the solution from the manual:

Can someone explain why we have to reverse the second equation? Shouldn't H2(g) be on the reactant side?

Posts: 54
Joined: Thu Jul 27, 2017 3:00 am
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Re: 8.61 Question

In the third equation there is already H2 on the reactants side; however, there are four moles of H2 in the third equation and you only want one mole in your final equation. Which is why you flip the second equation to cancel out 3 moles of H2 so you're only left with one mole in your final equation.