Order of reactions in kinetics In kinetics, zero order reactions are those reactions who are independent from the concentration of the reactant or the product. So their rate is equal to the constant k. But still we build the diagram where we find the correlation between concentration and time, where the slope is negative. 
Why do we even write a diagram to find the correlation between concentration and time, since these reactions are completely independent from concentration ?
So their rate is equal to the constant k.


With other words, the change of concentration over time is linear:

\[ \frac{d[\ce{A}]}{dt} = k\]