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8.25

Posted: Sun Jan 21, 2018 5:38 pm
by Andrea Grigsby 1I
for question 8.25, I understand everything up until the point where the answer key says Qreaction + Qcalorimeter =0, which then leads to the final answer. Can someone explain why the heat from the reaction + the heat of the calorimeter equals to 0?

Thanks :)

Re: 8.25

Posted: Sun Jan 21, 2018 5:54 pm
by Julian Krzysiak 2K
The regular heat equation for any system/surroundings is Qsystem=-Qsurroundings, because the amount of energy must be conserved between the 2 environments, due to the Law of the Conservation of Energy. In this case, the reaction=system, and surroundings=calorimeter, so Qreaction= -Qcalorimeter.
Then we can just play with the equation, by moving the Qcalorimeter to the other side, which would change the sign to positive, and we would get Qreaction+Qcalorimeter=0
(eg. X=-Y -->X+Y=-Y+Y --> X+Y=0)

Re: 8.25

Posted: Sun Jan 21, 2018 11:49 pm
by Andrea Grigsby 1I
oh yea, I completely forgot about that.
Thanks so much!

Re: 8.25

Posted: Wed Jan 24, 2018 4:23 pm
by Jana Sun 1I
I had a question on another part of this problem. When we're using q in our calculations, why is our q positive instead of negative (because the question gives us a negative q)? Is it because for the subsequent experiment with HBr and KOH, the temperature rises?