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The Second Book of General Ignorance - Corrections :-)

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Andrew Vaughan
776028.  Sun Jan 16, 2011 5:54 am Reply with quote

Being a pernickity so and so Ive done as asked and scribbled in the margins of the book when I felt something needed to be corrected or clarified. The posts that follow do that...

Page 8
While stiffness is a measure of compressibility the definition and units are not quite clear. Stiffness is described by Youngs modulus which is the ratio of stress (which has units of pressure; newtons/square metre or, indeed, Pascals) to strain (which is dimensionless). So the unit of stiffness is indeed the pascal. Compressibility however is defined as the relative volume change for a unit application of pressure and the units therefore are the reciprocal of Pascals.

Page 71
While it is true that Kekule initially believed that benzene consisted of a ring of six carbons attached to each other by alternating single and double bonds it was eventually realised that this would result in a distorted shape which would not be a ring as single and double bonds have different configurations and lengths. The accepted model now is that benzene consists of a uniform ring of carbons connected by single bonds with the other bond being a cloud of electrons circling above and below the ring.

To be precise, each carbon has 4 electons available for bonding. Three of these are used to bond to the neighbouring carbon atoms and one to a hydrogen atom. The remaining electron (in a 2p orbital) has been described as delocalised and does its bonding by interacting with the equivalent electron from its neighbouring carbon atoms.

 
Posital
776048.  Sun Jan 16, 2011 7:43 am Reply with quote

Yes - which is why it's generally drawn like this:

 

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