Reaction Rate Laws Rate laws are written with Rate=k[A]a [B]b. Where [A] and [B] are the concentrations of reactants A and B. (…or only A with 1 reactant.) The superscript is the order of the reactant and comes from the coefficient of the reactant. It tells how much affect changing the reactant has on the rate of reaction. k represents a rate constant that is the same for a particular reaction every time, regardless of the amount of A and B. The overall order of the reaction is = to the superscripts all added together.

Determining Reaction Order and Constant from Experimental Data Rates of reaction between NO and H2 at 800oC   Experiment      NO            H2         Initial Rate of Reaction  Number        moles/L     moles/L        moles/L sec     1                 0.001      0.004               0.002     2                 0.002      0.004               0.008      3                 0.004      0.001               0.008     5                 0.004      0.002               0.016   --------------------------------------------------------- When reaction rate changes the same as the concentration, that is 1st order… The power of the change for the reactant concentration = the multiple of rate change.

Reaction Rates and Reaction Mechanisms Instantaneous rates can be found by plugging in the concentrations of reactants into a rate law at a certain time.(See example problem 2 p579 in your text.) You can also construct a table from experimental data and take the slope of the tangent of the curve …slope = rise/run or [reactant]/seconds= reaction rate.

Reaction Mechanisms A reaction mechanism can be represented by a summation of the elementary reactions.

A Reaction Mechanism Summation See Example in Text Page 580.