Skill 9.8 Determining the rate law of a reaction from experimental data

Skill 9.8 Determining the rate law of a reaction from experimental data 

A rate law is an equation relating a reaction rate to concentration. The rate laws for most reactions discussed in high-school level chemistry are of the form  

If a reaction is zero order for a reactant, the concentration of that reactant has no impact on the rate as long as some reactant is present. If a reaction is first order for a reactant, the reaction rate is proportional to the reactant s concentration. 

For a reaction that is second order with respect to a reactant, doubling that reactant s concentration increases reaction rate by a factor of four. Rate laws are determined by finding the appropriate reaction order describing the impact of reactant concentration on reaction rate. 

Reaction rates typically have units of M/s (moles/liter-sec) and concentrations have units of M (moles/liter). For units to cancel properly in the expression above, the units of the rate constant k must vary with overall reaction order as shown in the following table. The value of k may be determined by finding the slope of a plot charting a function of concentration against time. These functions may be memorized or computed using calculus. 

---