1. Electromagnetic waves can transfer energy and carry information.

(a) State the relationship between the energy of a wave and its wavelength.

(b) Identify the region of the electromagnetic spectrum that can be used to obtain the concentration of Cr3+ ions in industrial waste waters.

(c) (i) Magnetic resonance imaging (MRI) is a technique in which radio waves are used to obtain an image of part or the whole of the human body.

Explain, on a molecular level, why this technique can be used to obtain information about the body.

(ii) Outline the information that MRI scans provide about the body.


2. The structure of an unknown compound A with empirical formula CH2 can be determined using information from a variety of analytical techniques.

(a) The mass spectrum of A is shown below.

(i) Determine the relative molecular mass of the compound from the mass spectrum and deduce the formula of the molecular ion.

(ii) Deduce the formulas of the fragments which give rise to peaks at m/z = 27 and 29.

m/z = 27:

m/z = 29:

(b) The infrared (IR) spectrum of A is shown below.

(i) Explain what occurs at a molecular level during the absorption of IR radiation by molecule A. 

(ii) Identify the bond responsible for the IR absorption at B. 

(iii) Deduce a structural formula consistent with the data. 

(c) (i) The IR spectrum was obtained using a double-beam spectrometer. The principal components of the instrument are shown below.

Describe the functions of C, D and E.




(ii) The range of absorbances between 1500–500 cm−1 is generally called the fingerprint region. Outline what happens on a molecular level when radiation in this region is absorbed, and suggest how the region is used in chemical analysis.


3. Paper chromatography and column chromatography can both be used to separate and analyse mixtures. Distinguish between the two techniques by completing the table below.




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