chemistry question help?

What energy in kJ is required to break 2.84 mol of NH3 into atoms? As noted below, this information can be used to calculate ΔH for gas-phase reactions.

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  • 8 years ago
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    You need a table of bond energies to do this. There's probably one in your book that you're supposed to use. I'll be using this one to solve your problem:

    http://wilenskychemistry.wikispaces.com/Thermodyna...

    It can be helpful to draw the structure to see exactly which bonds you're breaking. This one is pretty simple, you can easily tell that you're breaking 3 N-H bonds.

    So look at the Bond Energy table. You'll see that the energy required to break 1 mole of N-H bonds is 391 kJ.

    We have 2.84 moles. If the energy is 391 k per mol, we have to multiply by the number of moles. We also have 3 bonds, not just one. So we also need to multiply by 3.

    (391kJ)(2.84)(3) = 3330 kJ

    **that answer has already been rounded according to significant figures

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