Calculating atomic mass, A practical approach

Dalton published his first table of relative atomic weights containing six elements (hydrogen, oxygen, nitrogen, carbon, sulfur and phosphorus), relative to the weight of an hydrogen atom. Since these were only relative weights, they do not have a unit of weight attached to them.

The basic approach for measuring mass of an hydrogen atom is discussed below. The amount of electricity passed through the electrolyte is directly proportional to the mass of any substance deposited or liberated at an electrode, according to Faraday’s law of electrolysis.

        m = Z q ;     m - mass,  q - charge,  Z - constant of proportionality

        

The constant 'Z' can be experimentally determined by taking ratio of hydrogen liberated at electrode and the charge transferred q = I × t . It is approximately equal to 96500 gm/C. 

So the amount of charge required for depositing one hydrogen atom is same as the charge of an H+ atom that is q = 1.6 × 10^-19. Thus the mass of one hydrogen atom liberated at an electrode should be simply Z times q.  

        Atomic mass =  96500  × 1.6 ×10^-19     = 1.6 ×10^-27 kg