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E=mc^2 states mass and energy are interchangeable but ?

by jagdishdash
Tags: emc2, energy, interchangeable, mass, states
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jagdishdash
#1
Jan6-14, 12:39 PM
P: 11
But daltons law of constabt mass is voilated as states that while a reaction the mass of product = mass of reactant
any explainations?????
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jedishrfu
#2
Jan6-14, 12:50 PM
P: 3,094
I think you're mixing apples and oranges here. Einstein's E=mc^2 applies to nuclear reactions whereas Dalton's law applies specifically to chemical reactions.

In a chemical reaction, electrons are interchanged, bonds are made, others are broken and energy is either given off or absorbed but no nuclear reactions are happening.
jagdishdash
#3
Jan6-14, 01:01 PM
P: 11
Quote Quote by jedishrfu View Post
I think you're mixing apples and oranges here. Einstein's E=mc^2 applies to nuclear reactions whereas Dalton's law applies specifically to chemical reactions.

In a chemical reaction, electrons are interchanged, bonds are made, others are broken and energy is either given off or absorbed but no nuclear reactions are happening.

ok thankyou so much jedishrfu
my past 3 year doubt is now cleared thankyou so much

Enigman
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Jan6-14, 03:13 PM
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E=mc^2 states mass and energy are interchangeable but ?

Quote Quote by jagdishdash View Post
But daltons law of constabt mass is voilated as states that while a reaction the mass of product = mass of reactant
any explainations?????
An oxygen molecule is also stable, which is another way of saying that it takes energy E to pull two oxygen atoms apart. So you could think of the animation as representing a stable molecule. However, the binding energies of molecules are much less than those of nuclei, and so the masses involved are smaller. A typical chemical reaction might involve a nett energy of 30 kJ per mole, or 5 x 10-20 J per molecule. So the change in mass is 5 x 10-37 kg, which is only .0001% of the mass of an electron.
http://www.phys.unsw.edu.au/einstein...e5_binding.htm
In other words that change in mass is very small and hence negligible for molecules (not the same for nuclei-see link.).
1MileCrash
#5
Jan6-14, 04:03 PM
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There is no violation because since mass and energy are equivalent, Dalton's Law is truly saying that the total of mass and energy remain constant (since they are equivalent), which it does.
Borek
#6
Jan6-14, 04:32 PM
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Quote Quote by jedishrfu View Post
I think you're mixing apples and oranges here. Einstein's E=mc^2 applies to nuclear reactions whereas Dalton's law applies specifically to chemical reactions.

In a chemical reaction, electrons are interchanged, bonds are made, others are broken and energy is either given off or absorbed but no nuclear reactions are happening.
You are wrong. E=mc2 is not about nuclear reactions, it is about mass and energy equivalence. Yes, it is most easily observable in nuclear reactions, but it doesn't mean it doesn't hold for other systems.

In chemical reactions - strictly speaking - mass of products is NOT equal to mass of reactants when we take mass energy equivalence into consideration. However, the difference is many orders of magnitude lower than the accuracy with which we can weight substances involved, so for all practical purposes Dalton's law holds.


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