A system of physical chemistry - Index of

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A system of physical chemistry - Index of

BJERRUM'S THEORY

of oxygen are weak, and it is possible that hydrogen would exhibit a

band if its absorption were measured when the gas itself were excited,

i.e. at a fairly high temperature.

Molecular Heat of CO. 2. (SOg has the same molecular heat.)

As this is a triatomic molecule we have three atomic vibrations to

take account of. Two of these, however, may be expected to be the

same, as the oxygen atoms are presumably linked symmetrically to the

carbon atom. The translational energy plus the rotational energy are

in this case, according to Bjerrum, represented by the term 3RT, i.e.

3/2RT translational and 3/2RT rotational. The wave-length ol vibration

of each of the oxygen atoms with respect to the carbon is taken

by Bjerrum to be $'Ofx\ the wave-length of vibration of the two oxygen

atoms against each other is taken to be 8"i/i,. The formula employed

by Bjerrum is—

C„(o°, T°,) = 3R + 2R(^[5-o^] -J- Rc/,[8-i/.].

[Note that the second term on the right-hand side of this expression

contains the number 2, to allow for the fact that there are two

similar kinds of atomic vibrations present. It may also be pointed

out that if CO2 were a linear molecule, O = C = O, the rotational

energy term would be RT (as in a diatomic gas). The fact that the

value 3/2RT for the rotational energy agrees with experiment {cf. the

... .

constitution . being represented approximately by C^

following table) means that CO2 is not a linear molecule, its spatial

^o

The

con-

stitution of the COg molecule is considered in detail by Bjerrum ( Verh.

d. D.phys. Ges., 16, 737, 19' 4)-]

T Abs.

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