(2) (24 pts total) Ultrapure germanium, for use in semiconductors, is prepared b
ID: 560929 • Letter: #
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(2) (24 pts total) Ultrapure germanium, for use in semiconductors, is prepared by the following four steps: (1) Ge of "ordinary" purity is obtained by the high-temperature reduction of GeO2 with carbon; (2) this Ge is converted to GeCl by treatment with Cl2 and then purified by distillation; (3) GeCl4 is then hydrolyzed in water to GeO2; and (4) GeO2 is reduced with H2 to ultrapure germanium, which is then zone-refined. (a) (8 pts) Write balanced chemical equations for each of these four chemical steps using the smallest integer coefficients. (b) (8 pts) Evaluate AS (J/K) and Go (d) at 298.15 K for each reaction in part (a). (c) (8 pts) With respect to enthalpy and entropy changes, which reactions in part (a), i.e., (1)-(4), benefit from using high-temperatures and which benefit from using low-temperatures? Explain your choices Useful information not found in Appendix C of the textbook. SubstanceAH (kJ/mole) S° (J/mol-K) Ge(s) GeC1(D) GeO2(s) 31.1 245.6 39.7 -531.8 -580.0Explanation / Answer
a)
High temparature reduction GeO2 with Carbon.
GeO2(s) + C(g) ------------> Ge(s) + CO2(g)
Conversion of Ge in to GeCl4 by treating it with Cl2.
Ge + 2 Cl2 ----------> GeCl4
Hydrolysis of GeCl4 into GeO2.
GeCl4 +2 H2O ------------> GeO2 + 4 HCl
Reduction of GeO2 with H2.
GeO2 + 2H2 --------------> Ge + 2H2O
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