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1. A hypothetical A-B alloy of composition 55 wt% B-45 wt% A at some temperature is found to consist of mass fractions of 0.5 for both a and B phases. If the composition of the B phase is 90 wt% B-10 wt% A, what is the composition of the aphase? 2. An electrochemical cell is composed of pure copper and pure lead electrodes immersed in solutions of their respective divalent ions. a. For a 0.6 M concentration of Cu2+, the lead electrode is oxidized yielding a cell potential of +0.508 V. Calculate the concentration of Pb2+ ions if the temperature is 30*C. b. Compute the cell potential at 25°C and 1 M concentration in both half cells. Compare your results with the cell potential in (a). S 3. The room temperature electrical conductivity of a silicon specimen is 1000 (0-m) The electron concentration is known to be 8.87 x 1021 electron mAssuming the electron and hole mobility values are 0.14 m/.s and 0.05 m²/V. s, respectively. Note that the density of the silicon is 2.33 g/cm and its atomic mass is 28.09 g/mol. The electron charge is 1.6 x 10-19 Cand Avogadro's number = 6.023 x 102 atoms/mol. Answer the following questions: (a) Compute the hole concentration. (b) Calculate the number of free electron per atoms. (c) is the specimen n-type extrinsic, or p-type extrinsic? Why?