Question

Hydrogen gas is prepared by electrolyzing water at 25 degrees C. 152 mL of hudrogen are collected at a total pressure of 101 kPa. What is partial pressure of hydrogen under these conditions? How many moles of hydrogen were collected

Answer 1

The water electrolysis reaction is given as :

H2O = H2 + 1/2 O2

So one mole of water generates 1 mole of hydrogen gas and half mole of oxygen gas.

The partial pressure of the gas is directly proportional to the mole fraction of gas

So the partial pressure of hydrogen gas = ( 2/3) x 101

= 67.33 kPa

Using the ideal gas law , pV = nRT]

p = 67.33 kPa = 0.66453 atm

T = 298.15 K

0.66453 x 0.152 = n x 0.0821 x 298.15

n = 0.0041 moles

So 0.0041 moles of Hydrogen were collected