- #36
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Science Advisor
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Elaborating on the energy requirement issue-
I found a table which said bond energies in kJ/mol are:
H-H 436
O=O 499
O-H 463
So in order to approximate the energy requirements for 2 H20 --> 2H2 + O2, figure 4*463 to tear apart two water molecules, then get back 2*436 for the recombining hydrogen atoms plus 499 for the recombining oxygen atoms. The net energy required is thus 1,852 - 872 - 499 = 481. But a single water molecule would only require half that, 240.5 kJ/mol, to be split. This number is between the two numbers already given in this thread. This calculation ignores subtleties, such as that the O-H bond energy listed above would not apply exactly when the O already has another hydrogen attached to it.
I found a table which said bond energies in kJ/mol are:
H-H 436
O=O 499
O-H 463
So in order to approximate the energy requirements for 2 H20 --> 2H2 + O2, figure 4*463 to tear apart two water molecules, then get back 2*436 for the recombining hydrogen atoms plus 499 for the recombining oxygen atoms. The net energy required is thus 1,852 - 872 - 499 = 481. But a single water molecule would only require half that, 240.5 kJ/mol, to be split. This number is between the two numbers already given in this thread. This calculation ignores subtleties, such as that the O-H bond energy listed above would not apply exactly when the O already has another hydrogen attached to it.
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