Question

(a) Molten NaF is subjected to electrolysis. One of the half-reactions is 2 F- → 2 e- + F2 (g) How many faradays of electricity are required to produce 4.26 L of F2 at 742 torr and 20 °C? (b) If a current of 2.25 A is used, how many hours will it take to carry out the electrolysis in part (a)?

Answer 1

temperature = 20 + 273 = 293 K

pressure = 742 torr = .9763 atm

volume = V = 4.26 L

P V = n R T

.9763 x 4.26 = n x 0.0821 x 293

n = 0.173

2F- ---------------------> F2 + 2e-

1 mole F2 ---------------> 2 F electricity

0.173 mole F2 -------------> 2 x 0.173 = 0.3458 F

number of faradays = 0.3458 F

b)

q = 0.3458 F = 0.3458 x 96500 C = 33368.71 C

i = 2.25 A

i = q / t

2.25 = 33368.71 / t

t = 14830.54 sec

t = 8363 / 3600

t = 2.32 hours