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Topic: Calculating amount of heat  (Read 3075 times)

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Offline Ari

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Calculating amount of heat
« on: September 18, 2017, 02:48:58 PM »
I've been working on this problem and after trying to go through it twice I'm still getting the wrong answer. Not quite sure what I'm doing wrong. Can anyone help? Thanks in advance, Ari!

Calculate the amount of heat (in kJ) required to convert 65.6 g of water to steam at 100°C. (The molar heat of vaporization of water is 40.79 kJ/mol.)

Here's what I did:

Q1=65.6g x (4.18)x(100-0)
    =27420.8 J or 27.42kJ
Q2=65.6g x (1/18.02) x (40.79)
    =148.49kJ
Qtot= 27.42 + 148.49 = 175.9kJ

Offline Corribus

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Re: Calculating amount of heat
« Reply #1 on: September 18, 2017, 03:34:17 PM »
Ari,
Appreciate you showing work, but it helps if every quantity has a unit attached to make it a little easier to follow what you did. Your problem doesn't specify an initial temperature. It seems like you are using 0 degrees C, but it's not really clear if this is the value you should be using. From a literal reading of the problem as written, it seems like they want you to determine the amount of energy required to convert 65.6 g of water (at 100 deg. C) to steam (at 100 deg. C), in which case there would be no Q1, only the Q2 value.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Ari

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Re: Calculating amount of heat
« Reply #2 on: September 18, 2017, 05:34:44 PM »
You were right, I wasn't considering that T should be 100-100. Thanks for your help :)

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