Question

Electrolysis problem. Calculate the partial pressure of H2 (using barometric pressure and vapor pressure of water) and the Faradays required to generate 0.01358 moles of hydrogen gas given the following information.

10 mL of 3 M H2SO4 was diluted in 100 ml. 49.8 mL of this solution was used in electrolysis (initial buret reading was at 50 mL and final was at 0.2). The electrolysis was conducted at 20 V for seven minutes and forty seconds. I calculated the moles of H2 gas to be 0.01358 moles. An unknown metal strip in the solution went from an inital mass of 2.5675 g to a final mass of 2.3319 g. A loss of 0.2356 g. The barometric pressure in the room was 764.29 torr. The room temperature was 22.0 degrees Celsius or 295 K. The vapor pressure of water at this temp is 19.8 torr.

Answer 1

Electrolysis

From the given data set,

Partial pressure of H2 = barometric pressure - water vapor pressure at 22 oC

Using literature data,

Partial pressure of H2 = 764.29 - 19.8

                                    = 744.49 torr

Coulombs of charge = 20 x 460 = 9200 C

In faraday = 9200/96500 = 0.095 Faraday

So,

to generate 0.01358 mol H2 = 0.01358 x 0.095 = 0.003 Faraday's is required