A1. (a) One commonly used analytical technique is atomic absorption spectroscopy. State one use of this technique.
(b) The diagram below represents the components of an atomic absorption spectrophotometer.Identify the components marked X, Y and Z and explain their function in the analysis of a sample by this technique.
X – Name:
X – Function:
Y – Name:
Y – Function:
Z – Name:
Z – Function:
A2. The 1H NMR spectrum of X with molecular formula C3H6O is shown below.
(a) Deduce which of the following compounds is X and explain your answer.
CH3–CO–CH3 CH3–CH2–CHO CH2=CH–CH2OH
(b) Deduce which one of the peaks in the 1H NMR spectrum of X would also occur in the spectrum of one of the other isomers, giving your reasoning.
(c) The infrared and mass spectra for X were also recorded.
(i) Apart from absorptions due to C–C and C–H bonds, suggest one absorption,in wavenumbers, that would be present in the infrared spectrum.
(ii) Apart from absorptions due to C–C and C–H bonds, suggest one absorption,in wavenumbers, absent in this infrared spectrum but present in one of the other compounds shown in part (a).
(d) Suggest the formulas and m/z values of two species that would be detected in the mass spectrum.
A3. A sample of food colouring was analysed using thin-layer chromatography to check whether it contained a banned substance. The Rf value of the banned substance is 0.25 under the same conditions.
(a) State the number of components used to produce the food colouring.
(b) Identify a stationary phase commonly used in thin-layer chromatography.
(c) Identify the component in this chromatogram that has the greatest attraction for the stationary phase.
(d) Explain what is meant by the term Rf value.
(e) Predict where you would expect the banned dye to appear on the chromatogram and mark this spot with a circle on the diagram on the previous page.