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Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
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priyah priyah
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9 years ago
Part A
Mass of Mg(s)   0.31 g
Initial temperature of calorimeter contents   24.1 ºC
Final temperature of calorimeter contents     36.8 ºC

Part B
Mass of MgO(s)   1.22 g
Initial temperature of calorimeter contents   24.0 ºC
Final temperature of calorimeter contents   31.9 ºC

Calculate the molar enthalpies of reaction for the reactions occurring in Parts A and B
Help please!  Frowning Face
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Replies
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#1
9 years ago
The heat, Q, would be given by:

Q = -(mass of mixture in grams) * (heat capacity of mixture in joules per gram per degree Celsius) * (change in temperature in degrees Celsius)

The molar enthalpy is then Q/number of moles of solute.

You can calculate the change in temperature and the moles of solute, but you need the mass of solute plus HCl and the heat capacity of the mixture. You should have measured the former and the latter would have to be given to you or be looked up.
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#2
Staff Member
9 years ago
According to an internet source, the answer to this question is -601.6 KJ/mol Mg reacted
Ask another question, I may be able to help!
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#3
Educator
9 years ago
I've answer your question below, enjoy Smiling Face with Open Mouth
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#4
9 years ago
Hey bio_man,
I was looking over your answer and for some reason i am not getting the same answers as you when I calculate them.
Anyway you could explain it a little further for me? Thanks
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#5
Educator
9 years ago
No idea. It's not my assignment. Feel free to reject my post.
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Arii_bellArii_bell
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#6
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9 years ago
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#7
Educator
9 years ago
So, solved now? Smiling Face with Halo
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#8
9 years ago
Yes Everything should be good!
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