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Hi, I am able to do this question without the "80% of the heat released was absorbed by the water" part, and ended up getting 892.2g

How, does "80% of the heat released was absorbed by the water" affect the answer?

EDIT: I used the formula ((change in)$H)/n = (-mC$(change in)$T$)/$n$ to find the molar heat of combustion of ethanol. I got the mass of the water to be 892.2g.

Is it because molar heat is defined as the heat energy released by one mole of a substance undergoing combustion, and if only 80% released was absorbed, then I just multiply my answer by 0.8?

An explanation would be greatly appreciated, thankyou!

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  • $\begingroup$ Could you show your work? How much of the heat from ethanol combustion did you assume went into the water when you got your answer of 892.2g? $\endgroup$ – Curt F. Mar 8 '15 at 5:04
  • $\begingroup$ I made some edits $\endgroup$ – chemistryyo Mar 8 '15 at 5:13
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Is it because molar heat is defined as the heat energy released by one mole of a substance undergoing combustion, and if only 80% released was absorbed, then I just multiply my answer by 0.8?

Yes, this is exactly right!

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  • $\begingroup$ Can you elaborate on this just a bit? It has been flagged as low quality. $\endgroup$ – jonsca Apr 16 '15 at 22:43
  • $\begingroup$ Feel free to delete if you want. The OP asked a yes/no question, and I answered it. Not sure how more detail will help the OP. $\endgroup$ – Curt F. Apr 17 '15 at 0:22
  • $\begingroup$ Well, it's not so much about the OP as it is about someone looking for similar material in the future. It is your choice as to the fate of the answer, but adding in even a modicum of details would certainly bolster its value (incidentally, I did not downvote, that is automatically applied by the system) $\endgroup$ – jonsca Apr 17 '15 at 0:44
  • $\begingroup$ Feel free to suggest details to add or even better to edit my answer. To repeat myself, in my view, the question is answered; mission accomplished. $\endgroup$ – Curt F. Apr 17 '15 at 5:36
  • $\begingroup$ I hear ya, honestly. I'm not trying to be draconian or on your case about it, just trying to preserve something that's otherwise a good answer from getting flagged/downvoted, etc., because I know that it wasn't your intention just to answer for the sake of answering. I am going to leave it for now because it was accepted. $\endgroup$ – jonsca Apr 17 '15 at 23:23

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