Homework #8.55 Hess's Law

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Mary Becerra 2D
Posts: 53
Joined: Fri Sep 29, 2017 7:06 am

Homework #8.55 Hess's Law

Postby Mary Becerra 2D » Thu Feb 15, 2018 7:55 pm

I think there is a typo/error in #8.55. The solutions manual says to that the second reaction given (2Al + O2 ----> Al2O3) doesn't change its enthalpy value even though the book differs from the manual. Basically, the book says the second reaction is 2Al + O2 ----> Al2O3 while the solutions manual says it's
2Al + 3/2O2 ---> Al2O3. Can anyone else confirm?

Yashaswi Dis 1K
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

Re: Homework #8.55 Hess's Law

Postby Yashaswi Dis 1K » Thu Feb 15, 2018 10:35 pm

I am not entirely sure but whichever one has the correct balanced equation (I think it's the one in solutions manual?). It makes sense for 3/2 to be a coefficient for O2 to get 3 moles of oxygen in the product. Hope that helps a little!

Kailey Brodeur 1J
Posts: 34
Joined: Thu Jul 27, 2017 3:00 am

Re: Homework #8.55 Hess's Law

Postby Kailey Brodeur 1J » Fri Feb 16, 2018 10:15 am

I don't know if this is helpful, but the first equation you stated is the balanced chemical equation while the second one is the chemical equation utilized to find enthalpy of formation as the reactants are in amounts designed to produce exactly one mole of product.


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