Hi I'm trying to study for a test but cannot figure out how to solve these.
For GaAs, the autoionization constant at 300 K is 4x10^12 cm^-6.
a) What are the values of p and n, the hole and mobile electron carrier concentrations, respectively, at this temperature?
b) Suggest an element that might serve as a dopant, substituting for As, to increase n. Suggest an element that might serve as a dopant, substituting for Ga, to increase p.
c) If a donor is added that makes n= 2 x10^17 cm^-3, what is the value of p?
d)Propose reasonable concentrations of p and n for GaAs at 200 K and 400 K.
e) Will the autoionization equilibrium constant for GaN be larger or smaller than that for GaAs?
a)There are two samples, labelled A and B. Sample A is a physical mixture of GaP and GaAs in a 1:1 mole ratio. Sample B is a GaP0.5As0.5 solid solution. Are samples A and B distinguishable by elemental analysis, X-ray diffraction, absorption spectroscopy, or emission spectroscopy?
3. Recently, it has been found that many living systems use small gaseous molecules as hormones. A company that has strong interests in the control of fruit ripening has determined that a competitor is treating apples with a naturally occurring plant hormone that is generated at the apple orchards with small chemical reactors (the reactors appear to be small heaters with some sort of metal catalyst). The company has collected samples of the only reagent which goes into the reactor and samples of the product that is produced. You carry out gas chromatography, mass spectrometry, and carbon-13 NMR spectroscopy on each of the compounds.
a) The reactant put into the reactor is a compound that contains only C and H, exhibits one peak in the gas chromatogram, and has a mass spectrum with a peak at 56 amu. Draw the structures of three possible isomers that satisfy the octet rule and the mass spectrometry data; one isomer should have only single bonds.
b) For each of the isomers that you have drawn, identify the ideal bond angles for each carbon center on the drawing above.
c) The carbon-13 NMR exhibits just one peak. Identify which isomer of the three that you drew above is the reagent. Explain how you eliminated the others by identifying the number of peaks expected in the carbon-13 NMR spectra.
d) The product of the reaction yields a single peak in the gas chromatogram, has a peak at 28 amu in the mass spectrum, and exhibits one peak in the carbon-13 NMR. Draw the structure of the product.
e) The conversion of the reactant is found to be exothermic. Using bond strength data from your textbook and/or bond strain considerations, rationalize why the reaction is exothermic.
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