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Binding Energies

http://i57.tinypic.com/29ckhvs.png

For part b), i've found that the energy released is 17.6MeV, thus i thought that the binding energy for the RHS would be less than the LHS.

However for part d, the answer states that "The mass of the RHS is less, and the binding energy of the RHS is more".

I'm quite confused, how can this be?

Also, can someone clear up what binding energy is? I'm not quite sure what to picture when it is "released".
binding energy is the energy needed to split an atom into its constituent parts. The helium nucleus is much heavier than the hydrogen nuclei so more energy is needed to split it than the hydrogen nuclei.
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minnigayuen
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Original post by physicsftw
binding energy is the energy needed to split an atom into its constituent parts. The helium nucleus is much heavier than the hydrogen nuclei so more energy is needed to split it than the hydrogen nuclei.


That would be easy to tell if there was just one Hydrogen nucleus, but there are 2 nuclei, so i'm not sure how i am supposed to know that the Helium has more binding energy than both of Deuterium and Tritium combined.

Does the "energy released" in part b refer to a decrease in binding energy?
Original post by minnigayuen
That would be easy to tell if there was just one Hydrogen nucleus, but there are 2 nuclei, so i'm not sure how i am supposed to know that the Helium has more binding energy than both of Deuterium and Tritium combined.

Does the "energy released" in part b refer to a decrease in binding energy?


it doesnt say the helium nuclei has a higher binding energy than when 2 hydrogen nuclei combine. It's saying the binding nuclei of a helium atom is higher than the sum of binding energies of 2 individual hydrogen nuclei.
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minnigayuen
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Original post by physicsftw
it doesnt say the helium nuclei has a higher binding energy than when 2 hydrogen nuclei combine. It's saying the binding nuclei of a helium atom is higher than the sum of binding energies of 2 individual hydrogen nuclei.


Yes that's what i meant, i don't understand how i'm supposed to know how the total sum of the binding energies of the 2 individual hydrogen nuclei is less than the helium nucleus.
Original post by minnigayuen
Yes that's what i meant, i don't understand how i'm supposed to know how the total sum of the binding energies of the 2 individual hydrogen nuclei is less than the helium nucleus.


I guess this is one of the questions where they give you the answer and ask you how you would arrive at the answer. It's like in maths they give u an answer and they as you to show how you would get it. I think you just have to state the correct reason.
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minnigayuen
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Original post by physicsftw
I guess this is one of the questions where they give you the answer and ask you how you would arrive at the answer. It's like in maths they give u an answer and they as you to show how you would get it. I think you just have to state the correct reason.


Hm, even so, i wouldn't even know how those reasons make sense though :frown:

I just dont understand how to relate the question to the mark scheme


Here's a copy of the mark scheme for Part D:

Mass of RHS is less or gives off energy (1)
RHS has more binding energy or RHS more stable (1)
neutron has no binding energy (1)
Original post by minnigayuen
Hm, even so, i wouldn't even know how those reasons make sense though :frown:

I just dont understand how to relate the question to the mark scheme


Here's a copy of the mark scheme for Part D:

Mass of RHS is less or gives off energy (1)
RHS has more binding energy or RHS more stable (1)
neutron has no binding energy (1)


is this as or a2? which syllabus is it
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minnigayuen
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Original post by physicsftw
is this as or a2? which syllabus is it


A2, for wjec, if it helps
Original post by minnigayuen
A2, for wjec, if it helps



What i dont get is the question is asking you why the binding energy of helium is greater, but you get one mark by saying the right hand side has more binding energy. Isnt this just repeating the question?

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