P tupWat cih you cone luoue (2) (24 pts total) Ultrapure germanium, for use of \

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P tupWat cih you cone luoue (2) (24 pts total) Ultrapure germanium, for use of "ordinary" purity is obtained by the high-temperature reduction of CGeO wan hydrolyzed in GeCls by treatment with Cl, and then purified by distillation; (3) GeCl is then in semiconductors, is prepared by the following four steps: (1) Ge with carbon: (2) this Ge is converted to water to Ge0: and equations for each of these four chemical steps using the smallest integer ions in part (a). i.e., (1)-(4), benefit from (4) GeO, is reduced with H, to ultrapure germanium, which is then zone-reime (a) (8 pts) Write balanced chemical coefficients. (b) (8 pts) Evaluate AS(1/K) and G"(k) at 298.15 K fo (c) (8 pts) With respect to enthalpy and entropy changes, which react r each reaction in part (a). using high-temperatures and which benefit from using low-temperatures? Explain your choices r choices Useful information not found in Appendix C of the textbook. Substance AH (kJ/mole) Ge(s) GeCll) GeO:(s) S /mol-K) 31.1 -531.8 580.0 245.6

Explanation / Answer

a)

Step 1: Reduction of Ge

GeO2(s) + C(s) -------- Ge(s) + CO2(g)

Step 2: Reaction with Cl2

Ge(s) + 2Cl2(g) -------- GeCl4(s)

Step 3: Hydrolysis of GeCl4

GeCl4(s) + 2H2O(l) -------- GeO2(s) + 4HCl(l)

Step 4: Reduction of GeO2

GeO2(s) + 2H2(g) ------ Ge(s) + 2H2O(l)

(b)

Step 1: Reduction of Ge

GeO2(s) + C(s) -------- Ge(s) + CO2(g)

Delta H = Delta H(Products) - Delta H(reactants)

=> Delta Hf(CO2) - Delta H(GeO2)

=> -393.5 + 580

=> 186.5 kJ/mol

Delta S = Delta S(CO2) + Delta S(Ge) - Delta S(C) - Delta S(GeO2)

=> 213.64 + 31.1 - 39.7

=> 205.04 J/mol

Delta G = 186.5 kJ - (205.04)(298.15)/1000 = 125.367 kJ/mol

Step 2: Reaction with Cl2

Ge(s) + 2Cl2(g) -------- GeCl4(s)

Delta H = Delta H(Products) - Delta H(reactants)

=> Delta Hf(GeCl4) - Delta H(Ge(s))

=> -531.8 kJ/mol

Delta S = Delta S(GeCl4) - Delta S(Ge) - 2 * Delta S(Cl2)

=> 245.6 - 31.1 - 2 * 223

=> -231.5 J/mol

Delta G = -531.8 kJ + (231.5)(298.15)/1000 = -462.77 kJ/mol

Step 3: Hydrolysis of GeCl4

GeCl4(s) + 2H2O(l) -------- GeO2(s) + 4HCl(l)

Delta H = -580 - 4*92.31 + 2(285) + 531.8 = 152.56 kJ/mol

Delta S = 4*186.8+39.7 - 2(69.9) - 245.6 = 401.5 J/mol

Delta G = 152.56 - (401.5)(298.15)/1000 = 32.852 kJ/mol

Step 4: Reduction of GeO2

GeO2(s) + 2H2(g) ------ Ge(s) + 2H2O(l)

Delta H = 2(-285.8) + 580 = 8.4

Delta S = 2(69.9) + 31.1 - 245.6 - 2(130.6) = -335.9

c)

The reaction with Delta S>0 will be favored at high temperatures and the reaction with Delta H less tahn zero will be favored at low temperatures

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