A1. Spectroscopy involves techniques that can identify substances and determine their concentrations.

(a) Identify the atomic or molecular processes associated with the UV and microwave regions of the electromagnetic spectrum. 



(b) Atomic absorption (AA) spectroscopy is used for the detection of metal ions.

(i) Describe three principles of AA spectroscopy.

(ii) Besides the detection of calcium ions in blood, water or soil samples, state two other uses of AA spectroscopy. Your answer should list the detection of two different metal ions, each from a different source.

(iii) Explain how a student can determine the concentration of a metal ion in solution using AA spectroscopy.

A2. (a) One type of molecular vibration that occurs when CO2 molecules are exposed to IR radiation is illustrated in the diagram below.

Identify two other types of molecular vibrations that occur when CO2 molecules are exposed to IR radiation. Illustrate your answer with appropriate diagrams.

(b) Explain which molecular vibration of CO2 in (a) above is IR active and which is IR inactive.


A3. Nuclear magnetic resonance (NMR) and mass spectrometry are diagnostic techniques often used in the identification of organic compounds.

(a) Deduce two similarities and one difference in the 1H NMR spectra of the two isomers CH3COOH, a carboxylic acid, and HCOOCH3, an ester. 1H NMR data are given in Table 18 of the Data Booklet.



(b) The mass spectrum of one of the two isomers above has significant peaks at mass to charge ratios of 15, 45 and 60, while the other isomer has peaks at 15, 29, 31 and 60.Analyse these fragmentation patterns in the two mass spectra in order to distinguish between the two isomers.

(c) Outline how the technique of magnetic resonance imaging (MRI) is used in body scanners.




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