In an electrolysis cell similar to the one employed in this experiment, a studen

Question

In an electrolysis cell similar to the one employed in this experiment, a student observed that his unknown metal anode 0.208 g while a total volume of 96.30 mL of H_2 was being produced. The temperature in the laboratory was 25 degree C and the barometric pressure was 748 mm Hg. At 25 degree C the vapor pressure of water is 23.8 mm Hg. To find the equivalent mass of his metal, he filled in the blanks below. Fill in the blanks as he did. 1 mole H_2 requires passage of faradays No. of faradays passed = Loss of mass of metal anode = No. grams of metal lost per faraday passed = no. grams lost/no. faradays passed = g = EM The student was told that his metal anode was made of iron. MM Fe = g. The charge n on the Fe ion is therefore In ordinary units, the faraday is equal to 96, 480 coulombs. A coulomb is the amount of electricity passed when a current of one ampere flows for one second. Given the charge on an electron, 1.6022 times 10^-19 coulombs, calculate a value for Avogadro's number.

Explanation / Answer

Q1.

PH2 = 748-23.8 = 724.2 mm Hg = 724.2/760 atm = 0.95289 atm

VH2 = 96.30 mL = 96.30*10^-3 L

T = 25°C = 25+273 = 298 K

moles

n = PV/(RT) = 0.95289 * ( 96.30*10^-3) / (0.082 *298)= 0.00375525 moles

note that

1 mol of H2 --> 2 mol of e- --> 2 Faradays

then

0.00375525 moles -- > 0.00375525 *2 = 0.0075105 Faradays

loss of mass must be

mass = mol*MW = 0.00375525 *2 = 0.0075105 g is lost

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