27 To electroplate a metal shield with gold, the shield is placed in a solution

Question

27 To electroplate a metal shield with gold, the shield is placed in a solution containing gold ions (Au'), and an electric current is run through the solution from external wires (with one wire affixed to the shield). For each electron that passes through the system, a single gold atom is deposited on the surface of the shield. How much gold will be deposited if a 14.0-A current runs through the system for 19 minutes? [A gold ion, Au', has a mass of approximately 3.3 x 10-22 gl A) 16 g B 22 g C) 28 g D) 33 g E) 97 g i mol 3.3xlorro 28. A 1500-W heater is connected to a 120-V line. If the heater coverts electric energy entirely to heat energy, about how much heat energy does it produce in 2.0 hours of operation? A) 1.5 kJ B) 3.0 kJ C) 180 kJ Imin 1500 11,000 kJ E) 18,000 kJ

Explanation / Answer

(27) i = 14 A

t=19 min=1140 s

q= i t

q=14(1140)=15960 C

q= n e

n= 15960/(1.6x10-19)

n=9.975x1022

now mass=3.3x10-22(9.975x1022)

m=33 g

(28) E = P t

E=1500 (2x3600)=10800000J

E= 10800KJ= 11000 KJ

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