# First law of electrolysis

The amount of any substance deposited or dissolved at a particular electrode is proportional to the quantity of electricity utilized, i.e.,

w Q or w (I × t) or w = ZIt

where w is the mass of substance deposited or liberated in gram, Q is the amount of charge utilized in coulombs, I is the current strength in amperes, t is the time for which current flows through the cell in seconds, and Z is the electrochemical equivalent. Remember that Q is not the amount of charge passed, but it is the amount of charge utilized.

Electrochemical equivalent is the mass of substance deposited in gram either by passing one coulomb of charge or by passing one ampere of current for one second. Therefore,

# Second law of electrolysis

The amounts of different substances deposited or dissolved by the same quantity of electricity are proportional to their respective chemical equivalent weights.

It can be rearranged as

= Number of equivalents

∴  (as charge utilized is same)