A reaction is of zero order when the rate of reaction is independent of the concentration of materials. The rate of reaction is a constant. When the limiting reactant is completely consumed, the reaction stops abruptly.
The zero order rate law for the general reaction
is written as the equation
which on integration of both sides gives
When t = 0 the concentration of A is [A]0. The constant of integration must be [A]0.
Now the integrated form of zero-order kinetics can be written as follows
Plotting [A] versus t will give a straight line with slope -k.