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1 markEnergetics

CAPE Chemistry Unit 1 · 2006 · Paper 1 · Question 9(d)

The carbonyl group, >C=O, has absorption peaks in the region of 1680 to 1750 cm⁻¹, while the peaks for the alkene group, >C=C<, are manifested in the region of 1610 to 1680 cm⁻¹. What does this say about the bond energies of the >C=O and >C=C< functional groups?

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  1. 9(a)Infra red (IR) spectroscopy is widely used to determine the structure of molecules. State the principles upon which infra red (IR) spectroscopy is based.[3 marks]
  2. 9(b)Even though air consists of 78% N₂ and 21% O₂, these gases do not contribute to global warming. Explain this phenomenon.[2 marks]
  3. 9(c)Explain how the IR spectra may be used to distinguish between functional groups in organic compounds.[1 mark]
  4. 9(e)Suggest ONE reason why HCl has only one peak in its IR spectrum.[1 mark]
  5. 9(f)(i)Give ONE reason why the monochromator and sample cell are not constructed of glass or quartz.[1 mark]
  6. 9(f)(ii)What material may be used instead of quartz or glass?[1 mark]

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