2010年5月IB化学SL真题下载-Paper3
A1. Butan-1-ol, butan-2-ol, 2-methylpropan-1-ol and 2-methylpropan-2-ol are four structural isomers with the molecular formula C4H10O.
(a) Details of the 1H NMR spectra of two of these alcohols are given below.
Spectrum 1
Two peaks: One at 1.3 ppm (relative to the TMS reference) with an integration trace of nine units, and the other at 2.0 ppm with an integration trace of one unit.
Spectrum 2
Four peaks: The first at 0.9 ppm with an integration trace of six units.
The second at 1.7 ppm with an integration trace of one unit.
The third at 2.1 ppm with an integration trace of one unit.
The fourth at 3.4 ppm with an integration trace of two units.
Consider the proton environments present in each of the alcohol molecules when answering the following questions.
(i) Identify which alcohol gives spectrum 1 and explain your answer by stating which hydrogen atoms in the molecule are responsible for each of the two peaks.
(ii) Deduce which alcohol gives spectrum 2. Explain which particular hydrogen atoms in the molecule are responsible for the peaks at 0.9 ppm and 3.4 ppm.
(b) The mass spectrum of one of the alcohols shows peaks at m/z values of 74, 59 and 45.
(i) Deduce which two of the alcohols could produce this spectrum and identify the species responsible for the three peaks.
(ii) The spectrum also shows a significant peak at m/z = 31. Suggest which alcohol is responsible for this spectrum and deduce the species responsible for the peak at m/z = 31.
(c) Explain why the infrared spectra of all four alcohols are very similar.
A2. Atomic absorption spectroscopy can be used to determine the concentration of lead ions in a contaminated sample of drinking water.
(a) State one other use of atomic absorption spectroscopy.
(b) Describe the function of each of the following in an atomic absorption spectrophotometer.
The fuel:
The atomizer:
The monochromatic light source:
(c) A calibration curve was plotted using water with known concentrations of lead ions.
100 dm3 of the contaminated drinking water was reduced by boiling, to 7.50 dm3. It was found that when the reduced volume was tested it had an absorbance of 0.55. Calculate the concentration of lead ions (in mg dm–3) in the original contaminated drinking water.
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