Effect of reactant concentrations on rates

Let s start with a simple zero order reaction of the scheme 

For the general rate equation we can write Rate = + k (if we look at the product). 

The reason is simple - the rate of a zero order reaction is independent of the concentrations of any of the reactants. Although the reaction requires the presence of the reactants (otherwise there would not be a reaction), the rate of the reaction is always constant. 

In other words, if we changed the concentration of A in our experiments, the rate would still stay the same. 

Why am I telling you this Well, let s have a look at a first order reaction of the scheme 

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Equation (3.40) is quite general and describes the effect of reactant concentration on rate, not only at the start of the reaction in the complete absence of P (in the forward direction) or A (in the reverse direction), but also at any time during the approach to equilibrium (Alberty, 1959 Qeland, 1963, 1977). 

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