Re: chemical potential energy

On Nov 11, 11:17 am, Taras_96 <taras...@xxxxxxxxx> wrote:
Hi all,

A silly hypothetical situation my friend and I were discussing:

Suppose we have a method of converting any type of mass into energy,
as per the relation E=MC^2.

Now, suppose we have a mass of petrol.

Case 1: We burn the petrol, then convert the waste product from the
burning into energy using our hypothetical machine. In this case total
energy output is the energy from burning the petrol (chemical
potential energy stored in the bonds) and the energy from converting
the mass.

Case 2: We convert the unburnt petrol into energy, as per the relation
E=MC^2.

Now, case 1 has released more energy than case 2. Since energy/mass
can not be created or destroyed, where does the extra energy in case 2
go?

Taras

Total conversion of matter into energy was a concept popularized in
pulp science fiction novels (notably the Lensman series by E.E. "Doc"
Smith) MANY years ago.

Unburnt petrol has a chemical formula of (approximately) C8H18
(octane). Net weight about 114 units.

One molecule of octane, burnt, combines with 25 atoms of oxygen to
produce 8 CO2 molecules and 9 H2O molecules. Net weight about 514
units.

The added mass from the oxygen sucked out of the atmosphere is 400
units, over three times the weight of the fuel consumed.

Which will produce more energy - the total conversion of 114 units of
mass or the total conversion of 514 units of mass?

The chemical energy of the combustion is insignificant compared to the
thermonuclear output. It is so small that it would get lost in the
uncertainties of measuring the larger amounts.

Tom Davidson
Richmond, VA

.

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