Question

A dilute aqueous solution of Na2SO4 is electrolyzed between Pt electrodes for 3.65 h with a current of 2.89 A .

Part A What volume of gas, saturated with water vapor at 25∘C and at a total pressure of 744 mmHg , would be collected at the anode? The vapor pressure of water at 25∘C is 23.8 mmHg.

Answer 1

At anode reaction :

2 H2O   -----------> 4H+ + O2 + 4e-

current = 2.89 A

time = 3.65 h = 13140 sec

equivalent weight of O2 = 32 /4 = 8

w = E x i x t / 96485

   = 8 x 2.89 x 13140 / 96485

= 3.149 g

moles of O2 = 3.149 / 32 = 0.0984

pressure = 744 - 23.8 = 720.2 mmHg

               = 0.9476 atm

temperature = 298 K

P V = n R T

0.9476 x V = 0.0984 x 0.0821 x 298

V = 2.54 L

volume of gas = 2.54 L